Below in this subsection, a fairly simple scheme for diagnosing the most common failures is given. The causes of violations and their symptoms are grouped according to their relationship to the functioning of a particular unit or system: «Engine», «Cooling system» etc.
Regardless of the nature of the failure, the investigation of its cause is always based on the same basic principles:
Make sure you identify the symptoms of rejection correctly. The foregoing means confidence in determining the boundaries of the search area, which is especially important when diagnosing a failure to another motorist who cannot adequately state the symptoms of an existing violation.
Try not to overlook obvious violations. For example, if the engine won't start, feel free to check for fuel in the gas tank (at the same time, the statements of the owner of the faulty car should not be taken for granted). In the event of a failure of electrical equipment, first of all, you should check the condition and reliability of fastening of the terminal connections of the electrical wiring, only after that it makes sense to get diagnostic tools.
Try to address the cause of the failure, not its symptom. Replacing a dead battery with a new one will help start the engine, but the existing cause of the discharge of the old battery will remain uncorrected, which will lead to a quick failure of the new one. Similarly, replacing oil-stained spark plugs will allow the engine to function properly for a while, but the failure will certainly repeat itself soon (if the reason lay not simply in the use of candles of the wrong type).
Don't take any claims for granted! Please note that the newly installed «new» a component can also be faulty, especially if it has been in the trunk for a long time - you should not exclude a component from the list of checks just because it is new or recently installed. In case of neglecting the implementation of this recommendation, one should not be surprised when the reason for the failure, finally revealed, turns out to be lying on the surface from the very beginning.
Diagnostics of failures and reasons for the decrease in engine efficiency
Engine won't crank when trying to start it
- Faulty ignition switch.
- The pole terminals of the battery are oxidized, or the fastening of the wire lugs on them is loosened.
- The battery is discharged or defective.
- The correct functioning of the charge system is broken.
- The electrical wiring of the starting system circuit is broken or otherwise damaged, or the fastening of the terminals of the contact connections is loose.
- The traction relay or starter switch has failed.
- Starter motor defective.
- Broken or worn starter drive gear teeth or flywheel ring gear.
- The starter drive gear is wedged in the flywheel ring gear.
- Faulty start enable switch (models with AT) or starter open circuit switch (models with manual transmission)
- AT is not translated into position «R» or «N».
- Engine stuck (the crankshaft or camshaft is stuck, or one of the pistons has stuck on the wall of its cylinder), - try to turn it by hand on the crankshaft pulley bolt.
Engine cranks but won't start
Petrol models
- Startup is incorrect. Proceed as follows:
- Engage the parking brake;
- Engage neutral (RKPP) / move the selector lever to position «R» or «N» (AT);
- Without depressing the gas pedal, turn the key in the ignition lock to the right until it stops. Release the key as soon as the engine starts. If a warm engine cannot be started by cranking it with the starter for more than 4 seconds, slowly depress the gas pedal. Do not crank the engine for more than 30 seconds in a row, wait at least 15 seconds before trying again;
- At unstable speeds (e.g. misfires) in order to avoid failure of the catalytic converter, try to turn on the engine only for a short time and do not allow heavy loads, immediately drive the car to a Toyota service station;
- In areas where the outside temperature often drops below -20°C, it is recommended to install a coolant heater, a certificate on this issue can be obtained from any Toyota service station.
- Faulty or disabled engine immobilizer.
- Low battery (engine cranks too slowly).
- The fuel tank is empty or filled with low-quality fuel.
- Water has entered the fuel.
- The patency of the fuel lines is broken, the fuel pump is faulty, or the ventilation pipes of the fuel tank are blocked.
- The timing belt is broken or its tension is loose.
- The fuse for the electric fuel pump or the electronic injection system is defective.
- The air filter is heavily soiled. There are vacuum leaks in the air supply elements, malfunctions in the fuel injection and ignition control system.
- The battery terminal connections are oxidized or loose.
- The fuel pump is faulty, or its relay is damaged, check by ear that the pump is activated when the ignition is turned on.
- Faulty injector (s).
- Damaged or excessively wet components of the ignition system.
- Worn or defective spark plugs, or incorrectly set spark plug gap.
- Faulty ignition coil.
- The wiring to the ignition coil is broken or disconnected, or the wires are loose at the coil terminals.
- The electrical wiring of the starting system is broken or disconnected, or the fastening of the wires to the terminals is loose.
- The fuse of the engine control unit is damaged, any of the sensors is faulty: Hall, impulse sensor, coolant temperature sensor (ECT) or intake air (IAT).
- The compression pressure has fallen or is unevenly distributed between the engine cylinders.
- Valve clearances out of adjustment.
Diesel models
- Startup is incorrect. Proceed as follows:
- Engage the parking brake;
- Engage neutral (RKPP) / move the selector lever to position «R» or «N» (AT);
- Turn the key in the ignition switch to position II, the preheat indicator lamp on the instrument panel should light up (see relevant Section Instrument panel and signaling devices). The engine should be started no earlier than the control lamp goes out, without turning on the on-board consumers of electricity and without depressing the gas pedal, turn the key in the lock to the right until it stops. Note. At an outside air temperature below -10°C, you should also squeeze the gas pedal to the stop.
- Continue cranking the engine with the starter until the engine speed stabilizes, but no more than 30 seconds. Before restarting after an unsuccessful attempt, remember to first return the key to position 0 and wait at least 15 seconds;
- Watch the engine oil pressure indicator: the pressure indicator should be activated immediately after starting. When the engine is very cold, the pressure display does not appear until some time after starting. Do not increase the engine speed until the oil pressure indicator is activated;
- If the preheat control lamp does not light up, then there is a malfunction in the preheat system, which must be immediately repaired by a Toyota workshop;
- In areas where the outside temperature often drops below -20°C, the installation of a coolant heater is recommended. You can get help on this issue at any Toyota service station.
- Faulty engine immobilizer.
- The fuse of the electric fuel pump or preheating system is defective.
- The engine is not warmed up: check the correct operation of the preheater.
- There is no voltage at the solenoid shut-off valve. Connect a voltmeter or an LED probe to the switch. Turn on the ignition, the LED should light up, otherwise you need to find a break in the wiring and fix it.
- Solenoid shut-off valve defective. Check the reliability of the fastening of the electromagnetic switch, evaluate the condition of the contacts. Turn the ignition on and off, you should hear a click in the switch.
- There is damage in the fuel supply line or air in the lines:
- Pipelines or hoses are mechanically damaged or clogged, clean fuel lines and bleed air from lines and filter;
- The fuel filter is clogged, replace the filter element;
- In winter, check the filter and pipelines for ice or wax, drive the car into a heated garage, add gasoline to the system;
- Clogged tank vent or fuel intake strainer, clean.
- The adjustment of the moment of the beginning of the fuel supply is knocked down.
- The injectors are faulty, when the union nut of the fuel line of the faulty injector is loosened, the engine speed will not drop.
- Faulty high pressure fuel pump (injection pump).
- Compression pressure too low.
Difficulty starting a cold engine
- Low battery.
- The pole terminals of the battery are oxidized, or the fastening of the wire lugs on them is loosened.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- Faulty fuel supply system.
- There are fuel leaks through the injector (s).
- The compression pressure has dropped.
Difficulty starting a hot engine
- The air cleaner filter element is dirty, or its patency is otherwise impaired.
- Faulty fuel supply system (fuel is not getting to the injectors).
- Battery terminal connections oxidized (especially mass).
- The quality of the grounding of the power unit is violated.
- Serviceability of functioning of system of giving of fuel or management of the engine is broken.
- Serviceability of functioning of system of catching of fuel evaporations is broken (EVAP).
- The compression pressure has dropped.
Entering the starter into gear is difficult, or accompanied by extraneous noise
- Broken or worn starter drive gear teeth or flywheel ring gear.
- Loose or loose starter mounting bolts.
- Worn or damaged internal starter components.
Engine starts but immediately stalls
- Broken or otherwise damaged ignition circuit wiring, or loose terminals of the contact connections on the ignition module or generator.
- There is a fuel starvation of the injector (ov).
- The air cleaner element is dirty.
- There are vacuum losses.
- The idle speed setting is violated.
- There are intake air leaks or the vacuum lines are damaged.
- Valve clearances out of adjustment.
- Unsuitable oil is used (low viscosity).
- The compression pressure has fallen or is unevenly distributed between the engine cylinders.
- The setting of the ignition timing is violated.
- The valve timing settings are broken as a result of wear of the timing drive components.
During parking, oil leaks under the engine
- There are leaks from the oil pan gasket or drain plug.
- There are leaks through the seat seal of the oil pressure switch.
- There are leaks from the cylinder head gasket.
- There are leaks through the engine shaft seals.
- There are leaks in the oil pump.
Idle speed stability is broken
Petrol models
- There are vacuum losses. Make sure that the fixing bolts/nuts are securely tightened, check the fact and quality of fastening on your fittings on the inlet pipeline of all vacuum hoses. Listen to the running engine with a stethoscope or a piece of fuel hose. The presence of a hissing sound will reveal the source "leaks" vacuum. No less effective can be used for checking a solution of soapy water.
- There is a malfunction of the functioning of the components of the power system.
- The ignition system malfunctioned.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- Faulty exhaust gas recirculation valve (EGR).
- The patency of the PCV valve is broken.
- Air filter blocked.
- The thermostatic air cleaner is malfunctioning.
- The fuel pump is not supplying enough fuel to the injection system injectors.
- The patency of the injector is broken (ov).
- There are leaks from the cylinder head gasket, measure the compression pressure in the engine cylinders.
- Worn timing belt.
- Camshaft lobes worn out (ov).
- Valve clearances out of adjustment.
- The valves are burnt out, or loosely pressed against the saddles.
- The setting of the ignition timing is violated.
- The compression pressure has fallen or is unevenly distributed between the cylinders.
- The idle speed setting is violated.
Diesel models
- The quality of the connections of the fuel hoses on the injection pump and the fuel filter is broken.
- Mechanically damaged or loose fastening of the high-pressure fuel pump.
- The connections of the return pipeline and the fuel supply pipeline are reversed.
- There is a damage in the fuel supply line:
- Pipelines or hoses are mechanically damaged or clogged, clean the fuel pipes;
- Fuel filter clogged. Replace the filter element;
- In winter, check the filter and pipelines for ice or wax, drive the car into a heated garage, add gasoline to the system;
- Clogged tank vent or fuel intake strainer, clean.
- The adjustment of the start of fuel supply is knocked down.
- The injectors are faulty, when the union nut of the fuel line of the faulty injector is loosened, the engine speed will not drop.
- Faulty high pressure fuel pump (injection pump). Install a new or known-good injection pump for testing.
There are misfires at idle
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- Faulty spark plug wires.
- Moistened or damaged components of the ignition system.
- There is a short in the ignition circuit.
- The quality of the contact connections of the explosive wires is broken, or the ignition module is faulty.
- Faulty ignition coil.
- The components of the toxicity reduction system are faulty, or the patency of the corresponding tract is impaired.
- There are leaks in the EGR valve.
- The patency of the fuel filter is broken, or the fuel is contaminated.
- There are vacuum losses.
- RPM or idle mixture quality settings are violated.
- The setting of the ignition timing is violated.
- The compression pressure has fallen or is unevenly distributed between the cylinders.
- There is a loss of vacuum in the intake manifold or through the connecting vacuum hoses.
- The patency of the fuel injectors is broken.
Misfire occurs while driving in gear
- The patency of the fuel filter / connecting path of the power system is broken.
- The fuel pressure has dropped.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- The setting of the ignition timing is violated.
- The reliability of the fastening of the contact connections of the explosive wires is broken, or the ignition module is faulty.
- Occurs «breakdown» wiring BB spark plug wires.
- Components of systems of decrease in toxicity of the fulfilled gases are faulty.
- The compression pressure has fallen or is unevenly distributed between the cylinders.
- The ignition system is faulty, or the contact connections of its electrical wiring are loose.
- There are vacuum losses.
- The fuel pump is faulty, or the pressure it develops has dropped.
- The ventilation of the fuel tank is broken.
Excessively high idle speed
- The smoothness of the throttle actuator is broken.
- The idle speed setting is violated.
- There are leaks in the intake air path.
- The correct functioning of the engine management system is broken.
Decreased or undercharged battery
- The alternator drive belt is worn out, or the adjustment of its tension force is broken.
- The pole terminals are oxidized, or the fastening of the wire lugs on them is loosened.
- The level of electrolyte in the banks has dropped.
- The generator does not produce the required charge current.
- The electrical wiring of the charge system circuit is broken or otherwise damaged, or the fastening of the terminals of the contact connections is loose.
- The battery is being discharged due to a short circuit in the onboard wiring.
- There is an internal defect in the battery.
Ignition/charge warning lamp stays on while engine is running
- There is an internal defect in the generator or voltage regulator.
- The alternator drive belt is worn or broken, or the adjustment of its tension force is broken.
- Worn, jammed or dirty alternator brushes.
- Weak or broken alternator brush springs.
- The charge circuit wiring is broken, or the terminal connections are loose.
The ignition/charge warning lamp does not light up when the key is turned to the ON position
- The filament burned out.
- The printed circuit board of the instrument cluster is faulty, or the lamp holder is faulty.
- Generator defective.
There are misfires while driving
- The patency of the fuel filter is broken, or the fuel is contaminated.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- The setting of the ignition timing is violated.
- Serviceability of functioning of components of system of decrease in toxicity of the fulfilled gases is broken.
- The compression pressure has fallen or is unevenly distributed between the cylinders.
- Faulty ignition coil.
- The ignition system malfunctioned.
- There is a loss of vacuum in the intake manifold or through the connecting vacuum hoses.
- Violated patency of the injectors.
- There are leaks in the EGR valve.
- The idle speed setting is violated.
The stability of the engine speed is violated during acceleration
- The ignition system malfunctioned.
- The setting of the ignition timing is violated.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- The patency of the fuel filter is broken.
- The patency of the fuel injectors is broken.
- The fuel pressure has dropped as a result of a malfunction in the functioning of the fuel pump or the patency of the fuel lines.
- The serviceability of the functioning of the injectors, or the engine management system is broken.
- Loose connector fastening (ov) fuel injector wiring.
- There are air leaks in the intake tract.
- The EGR system malfunctioned.
The engine runs jerky when the accelerator pedal is held motionless
- There are air leaks in the intake tract.
- Faulty fuel pump or fuel pressure regulator.
- Loose connector fastening (ov) fuel injector wiring.
- There are malfunctions of the engine management system.
The engine spontaneously stalls
- The idle speed setting is violated.
- The patency of the fuel filter is broken, or moisture has got into the power system.
- Moistened or damaged components of the ignition system.
- Components of systems of decrease in toxicity of the fulfilled gases are faulty.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- Faulty spark plug wires.
- There are vacuum losses at the throttle body, intake manifold or through the connecting hoses.
- Valve clearances out of alignment.
- The fuel pump is faulty, or the pressure it develops has dropped.
- The ventilation of the fuel tank is broken, or the fuel lines are blocked.
- Serviceability of functioning of system of injection or management of the engine is broken.
Decreased engine power
- Damaged crankcase ventilation hose.
- Damaged vacuum hose.
- Damaged intake manifold gasket.
- The setting of the ignition timing is violated.
- Damaged spark plug wires or ignition coil.
- Spark plugs are worn or damaged, or the electrode gap setting is broken.
- The correct functioning of the fuel supply system is broken.
- Air cleaner element blocked.
- The brakes are jammed.
- The level of ATF in AT has fallen.
- Oil pressure dropped.
- Clutch slips (RKPP).
- The patency of the fuel filter is broken, or moisture has got into the power system.
- The EGR system malfunctioned.
- The car is filled with non-standard fuel.
- Compression pressure dropped or unevenly distributed between the cylinders
- Disturbed patency of the exhaust tract.
- The fuel pump is faulty, or the pressure it develops has dropped.
- There are leaks in the intake air path.
- Serviceability of functioning of system of injection or management of the engine is broken.
- The engine is overheated.
- The engine has not warmed up to normal operating temperature.
Happening «shots» in the exhaust tract
- The EGR system malfunctioned.
- The setting of the ignition timing is violated.
- The air cleaner thermostat is malfunctioning.
- There are vacuum losses.
- Valve clearances out of alignment.
- Damaged valve springs or «sticking» valves.
- There are leaks in the intake air path.
- There is a malfunction in the secondary (BB) ignition circuit (candle insulators, BB wires, ignition module).
- The correct functioning of the fuel supply system is broken.
The engine runs jerky when the accelerator pedal is held motionless
- There are air leaks in the intake tract.
- Fuel pump defective.
- Loose connector fastening (ov) fuel injector wiring.
- There are malfunctions of the engine management system.
During acceleration or when the load on the engine is increased, there are knocks caused by too early ignition or detonation
- The vehicle was filled with the wrong grade of fuel.
- The setting of the ignition timing is violated.
- There is excessive carbon formation in the combustion chambers.
- Custom spark plugs installed.
- The correct functioning of the fuel supply system is broken.
- Damaged BB wires.
- The EGR valve is malfunctioning.
- There are vacuum losses.
- Faulty knock sensor.
- Valve clearances out of adjustment.
- Worn or damaged valve springs.
- There is a mechanical failure of the valve drive components (rocker arms, rocker axles, etc.).
The engine continues to run after the ignition is turned off (diesel effect)
- There are leaks in the injectors.
- Excessively high idle speed is set.
- Engine operating temperature is too high.
- The setting of the ignition timing is violated.
- There is excessive carbon formation on the bottoms of the pistons.
- going on «sticking» valves.
- Valve clearances set incorrectly.
- The EGR system malfunctioned.
There is a drop in engine oil pressure
- The oil level has dropped, or the wrong grade of oil has been filled.
- Worn engine bearings and/or oil pump.
- The engine is overheating.
- Oil filter blocked.
- The patency of the mesh filter of the oil intake is broken.
- Excessively low idle speed is set.
- There was a short circuit in the braid of the onboard electrical wiring.
- Defective oil pressure gauge.
Excessive consumption of engine oil
- Loose oil pan drain plug.
- Damaged crankcase ventilation hose.
- Faulty crankcase ventilation valve.
- The pan mounting bolts are loose, or its sealing gasket is damaged.
- The front cover mounting bolts are loose or the sealing gasket is damaged.
- Damaged crankshaft seal.
- The cylinder head cover bolts are loose or the gasket is damaged.
- Loose oil filter seat.
- The tightening force of the oil pressure switch has loosened.
- There is excessive wear on the pistons or cylinders.
- Worn or damaged piston rings.
- Worn or damaged valve stem seals for intake and/or exhaust valves.
- Worn valve stems.
- Worn or damaged valve guides.
Excessive fuel consumption
Petrol models
- The air cleaner filter element is dirty or otherwise obstructed.
- There are leaks in the intake air path.
- The setting of the ignition timing is violated.
- The idle speed setting is violated.
- There are leaks in the fuel line.
- Violated patency of the injectors.
- Serviceability of functioning of system of injection of fuel or management of the engine is broken.
- Serviceability of functioning of systems of decrease in toxicity is broken.
- Insufficient tire inflation pressure, or wrong wheel size fitted.
- «tacked on» brakes.
Diesel engine
- Clogged return line. Blow out the return line from the injection pump to the fuel tank with air.
- Excessively high idle speed and maximum speed.
- The engine has mechanical damage. Check compression, repair engine if necessary.
There are fuel leaks (in the cabin and near the car distinctly smells of gasoline)
- Damaged mechanically or as a result of corrosion development of the fuel tank, fuel lines or their union connections.
- The fuel tank is full.
- EVAP charcoal canister filter blocked.
- There are leaks in the EVAP system path.
- Damaged or excessively worn internal injector components.
- The fuel injection system malfunctioned.
Various kinds of noises that occur during engine operation
- A loud thud, more likely to occur during acceleration, indicates worn or damaged main bearings, or uneven crankshaft wear.
- Similar to the above, but slightly higher frequency, the sound that also occurs more often during acceleration indicates a possible wear of the connecting rod bearings.
- An overlapping metallic knock that increases with engine speed and weakens as the latter warms up indicates excessive wear on the pistons and cylinder walls.
- Frequent clicking, which increases with acceleration, indicates wear on the piston pins or nests for their fit in the pistons (sound occurs each time the corresponding piston passes TDC).
- A metallic clicking sound from the water pump indicates worn bearings and the need to replace the pump assembly.
- The cause of frequent knocking or clicking, which increases with increasing speed, may be a violation of the adjustment of valve clearances - listen to the valve mechanism with a stethoscope / piece of vacuum hose. If adjusting the valves does not correct the situation, the condition of the hydraulic tappets and other components of the valve mechanism should be checked.
Note. In some cases, the elimination of knocking is helped by filling the engine with oil with a higher viscosity coefficient.
- The cause of a uniform metallic knock or rumble emitted by the timing drive on 3.0 L models may be wear on the gas distribution chain or a violation of its tension adjustment; also check the condition of the sprockets.
Diagnosis of malfunctions of the cooling system
The engine is overheating
- The coolant level has dropped.
- The timing belt is damaged or its tension is not adjusted
- The accessory drive belt is dirty with oil.
- The patency of the water or air paths of the radiator is broken.
- There are coolant leaks from the radiator.
- Water pump defective.
- Faulty thermostat.
- Poor quality coolant filled.
- There is a malfunction in the fan circuit (ov) cooling systems.
- There is mechanical damage to the impeller of the cooling fan.
- The tightness of the radiator cap is broken.
- The setting of the ignition timing is violated.
- There is an over-depletion of the air-fuel mixture.
- The clutch is slipping.
- «tacked on» brakes.
- Incorrect distance between piston and cylinder wall.
- The cooling system path is blocked by an air lock.
- Wrong type of gear oil filled.
- Exhaust tract resistance too high (high back pressure).
- Inaccurate temperature readings.
There is hypothermia
- Faulty thermostat.
- Inaccurate temperature readings.
- There is a malfunction in the cooling fan circuit.
There are external coolant leaks
- The hoses of the cooling path are mechanically damaged or destroyed as a result of aging of the material, or the clamps of their fastening are loosened.
- Worn or damaged water pump seals (coolant will seep through the check hole).
- There are coolant leaks from the radiator or expansion tank.
- Damaged drain or squeeze plugs in the water jacket of the engine block.
- The tightness of the landing of the sensor-switch of the coolant temperature is broken.
- Block/cylinder head gaskets damaged or casting cracked.
- Thermostat cover damaged.
- Radiator cap defective.
- The coolant has boiled as a result of overheating.
There are internal coolant leaks
Note. The presence of internal leaks is confirmed by the presence of coolant in the engine oil, causing the latter to emulsify.
- Broken cylinder head gasket.
- Cracked cylinder head or block.
- Loose cylinder head bolts.
There is a loss of coolant
- Too much coolant has been added to the system.
- The coolant boils away as a result of overheating.
- There are external or internal coolant leaks (see above).
- Radiator cap defective.
- The pressure in the cooling system rises due to compression in the cylinders as a result of cracks in the head or block, or a violation of the integrity of any of the seals.
Coolant circulation interrupted
- The water pump is faulty - check by probing the upper radiator hose.
- The patency of the cooling tract is broken.
- Loose water pump drive belt.
- Stuck thermostat.
- The coolant level has dropped.
Corrosion develops
- Excessively contaminated coolant - add only distilled rainwater to the system.
- Antifreeze too diluted.
- The coolant is not often replaced and the path is flushed.
Troubleshooting AT
Note. In view of the complexity of the AT design, it will be difficult for an average amateur mechanic to accurately diagnose its failures and restore repairs. In the event of problems other than those listed below, the car owner should seek help from car service specialists. You should also not rush to dismantle a faulty transmission, as many of its checks are made in situ (at the regular place).
ATF leaks
- ATF is usually dark red in color - do not confuse traces of its leaks with those from engine oil (the latter can be carried to the transmission crankcase by the oncoming air flow).
- To identify the source of the leak, first of all, clean the transmission case and its surrounding surfaces from dirt and grease. Use a quality degreaser or steam clean the unit. Take the car for a short trip at low speed (so that traces of an existing leak are not carried far from its source). Jack up the car and place it on jack stands. Inspect the transmission case, visually identifying sources of ATF leakage. Most often these are:
- Transmission oil pan: Tighten fasteners and/or replace gasket;
- Transmission rear extension: tighten fasteners and/or replace oil seal;
- Filler neck: replace the rubber seal at the point where the filler neck enters the transmission case;
- Ventilation tube: transmission is overfilled and/or water has entered the crankcase;
- Speedometer connection unit: replace the O-ring at the entry of the drive cable into the transmission case.
ATF is brown or smells like burning
- The ATF level in the transmission has dropped, or the fluid is burnt and needs to be replaced.
- Faulty overdrive clutch.
- 2/4 gear brake band defective.
- Defective clutch of lower and reverse gears.
- Reverse clutch defective.
Having problems shifting gears
In Chapter Gear box describes the procedure for checking and adjusting the AT gear selector drive. The following are the most common problems that can be associated with drive misalignment:
- The engine is started in a position other than «R» or «N»;
- The transmission position displayed on the indicator panel differs from the one actually selected;
- The vehicle is driven with the transmission in position «R».
Transmission does not automatically downshift when the gas pedal is fully depressed
- Throttle cable misadjusted when kick-down is engaged.
The engine is started in a transmission position other than «R or «N»
- The start enable switch is defective, or its adjustment is violated.
- Defective gear selector lever or gear selector drive.
Transmission «jumps off» from the selected position, shifting is difficult or noisy, or does not ensure the forward movement of the car forward or backward
- There are many possible causes of these failures, but only one of them falls within the purview of the average amateur mechanic - an ATF level violation. Check, if necessary, adjust the level / replace the fluid and filter, in parallel check the condition of the ATF. In all other cases, the car should be driven away for diagnostics and reconditioning / replacement of the transmission to a service station.
Diagnosis of cardan shaft malfunctions
There are leaks at the front of the propeller shaft
- Damaged or worn transmission rear oil seal. Also check the condition of the sliding collar surface.
When you turn on the transmission (at the moment of loading) there is a knock
- Loose rear suspension components.
- Sliding clamp spindle worn.
- Loose propshaft bolts/nuts.
- Worn or damaged universal joint bearings (ov).
- Worn center bearing/center support cushion.
There is a metallic rattle, consistent with the speed of the car
- Worn cardan bearings (ov).
There are vibrations
Note. First of all, check the wheel balance and tire inflation pressure. Usually the vibrations increase with the increase in motion.
- Install a tachometer in the passenger compartment and while driving, try to determine the engine speed at which the vibration reaches its maximum intensity, then shift the gear and bring the engine speed to the same value.
- If vibration occurs and reaches its maximum intensity at the same engine speed, regardless of the selected gear, its source is not the cardan shaft, since its rotation frequency depends on the choice of gear ratio.
- If a gear change causes the vibration to disappear or noticeably decrease its intensity (at the same engine speed), you should proceed to check the condition of the cardan shaft:
- Check the cardan shaft for signs of bending and other deformations, replace if necessary;
- Thoroughly clean the shaft, - adhering dirt can cause imbalance;
- Assess the degree of wear of the bearings of the cardan joints, if necessary, replace the assemblies;
- Check the balance of the cardan shaft or its connecting flange. Make sure that the balancing weights are in place, remove the shaft and install it by turning it 180°- if the vibrations do not disappear, give the shaft to balancing;
- Check up reliability of a tightening of fixing bolts/nuts;
- Assess the degree of wear of the central bearing;
- Check the condition of the rear transmission bushings.
There is a scraping sound
- Make sure the sliding yoke dust cover does not rub against the transmission rear extension housing.
There is a howl or whistle
- The source of such sounds may be the central bearing.
Diagnosis of malfunctions of the rear axle and final drive
There is extraneous noise, the same when driving in gear and coasting
- Natural road noise.
- Excessive differential gear play.
- Excessive hypoid gear play.
- Loose or missing pinion nut.
- Worn or incorrectly inflated tires.
- Worn or damaged wheel bearings, or their tightness is loose.
- The oil level in the differential dropped.
- Differential defective.
There is a knock that occurs when starting off or when shifting gears
- The differential is faulty or its adjustment is broken.
Extraneous sounds occur when making turns
- Differential defective.
There are vibrations
- See the subsection on diagnosing driveshaft problems. If the shaft is in order, jack up the rear of the car and place it on props and manually assess the condition of the wheel bearings, replace if necessary.
There are oil leaks
- Main gear drive gear seal damaged.
- Damaged axle seals.
- Loose fasteners or damaged differential cover gasket.
- Loose differential drain or fill/check plug.
- The patency of the ventilation breather of the differential is broken.
Transfer case troubleshooting
Gears jump out of gear
- The amount of free travel of the control lever is violated.
- The control lever clings to the console.
- The fasteners of the transfer box suspension supports are loose, or fatigue deformation of the material occurs.
- Worn internal components of the transfer case, or the adjustments are violated.
Difficulty switching modes
- The oil level has dropped.
- Worn internal components of the transfer case, or the adjustments are violated.
There are extraneous noises
- The oil level in the transfer case has dropped.
- The presence of noise when selecting any of the modes indicates a malfunction in the components of the rear differential or rear axle.
Diagnostics of malfunctions of the brake system
Note. Before concluding that the brake system has failed, check the condition and inflation pressure of the tires, the vehicle's load evenness, and the front wheel alignment.
When braking, the directional stability of the car is violated
- Tires incorrectly inflated.
- The adjustment of the angles of installation of the front wheels is broken.
- One vehicle axle (front or back) Fitted with wheels of different sizes.
- Worn, damaged or oily brake pads / shoes from one of the sides of the car.
- Excessively worn brake pads or a disc from one of the sides of the car.
- Loose fasteners of the front suspension components.
- One or more brake mechanisms are faulty.
- Broken brake lines.
- Loose caliper or brake shield mounting bolts.
- The caliper/wheel cylinder piston of one of the brake mechanisms is stuck, or its movement is difficult.
- Brake pads / shoes with friction linings of various types are installed on different sides of the car.
- Worn or damaged steering or suspension components.
- The wheel bearing preload is out of adjustment.
Extraneous noises occur during braking (grinding or high-frequency squealing)
- The friction linings of the brake pads of the front wheels are worn out - the sound is emitted by the wear sensors of the pads.
- Dirty or polished brake pads.
- Oil spilled on the working surface of the brake pad (clicks are heard).
- Damaged brake disc / drum - usually after a long parking of the car.
- A foreign object has fallen between the disc and the shield of the brake mechanism (e.g. stone).
- The brake shield is deformed.
Excessive brake pedal travel
- There is a local violation in the brake system.
- The hydraulic fluid level in the GTZ reservoir has dropped.
- Air has entered the hydraulic system.
- Serviceability of functioning of automatic regulators of brake mechanisms is broken.
- Defective restrictor valve.
- Faulty GTC.
- The vacuum brake booster is faulty.
There is a softness of the brake pedal when it is squeezed out
- Air has entered the hydraulic system.
- Flexible brake hoses damaged as a result of material aging.
- Loose fasteners GTZ.
- Faulty GTC.
- The setting of the working clearances of the brake pads / shoes is violated.
- The patency of the ventilation hole of the GTZ reservoir cover is broken.
- Deformed rubber brake lines.
- Caliper seals softened.
- Brake fluid needs to be replaced.
Applying too much force to the brake pedal is required to stop the vehicle
In addition to the reasons listed in the previous subsection:
- The vacuum brake booster is defective.
- Friction linings of brake pads/boots are excessively worn.
- Piston stuck (And) caliper/wheel cylinder.
- Friction linings of brake pads/boots contaminated with oil or grease.
- Damaged or worn brake discs.
- Faulty GTZ or caliper (s) / wheel cylinder (s).
- Recently installed and did not have time to run in new brake pads / shoes.
- There is a local violation in the brake system.
Foot brake pedal sinks to the floor with no resistance
- The fluid level in the GTZ reservoir has dropped, or there are leaks through the pistons of the calipers / wheel cylinders.
- Brake lines damaged or loose fittings.
During braking, the foot brake pedal pulsates
- Worn or damaged wheel bearings or misadjusted preload.
- The brake caliper components are installed incorrectly, or foreign objects have fallen between them.
- Excessive brake disc lateral runout/drum ovality.
- Brake pads worn unevenly.
There is a pulsation of the foot brake pedal when it is squeezed out during hard braking
- A consequence of the correct functioning of the ABS.
During braking, vibration is transmitted to the brake pedal or steering wheel
- There is excessive brake disc runout/brake drum deformation.
- Friction linings of brake pads/boots are worn out.
- Loose caliper/brake plate mounting bolts.
- Worn suspension or steering components or bearings.
Brakes «seized» (reduced efficiency of the engine output, the wheels heat up excessively while driving)
- Adjustment of an output rod of a pedal of a foot brake is broken.
- The patency of the GTZ inlet fitting is broken.
- The GTZ piston is stuck in the cylinder.
- Excessively worn brake pads/boots.
- The piston cups in the main brake cylinder or brake calipers are deformed.
- Parking brake adjustment out of order.
- The wheel bearing preload is out of adjustment.
- The adjustment of the installation height of the foot brake pedal is broken.
- Stuck wheel cylinder (s).
- The adjustment of the clearances of the landing of the shoes in the drums of the brake mechanisms is violated.
- Faulty GTC.
- Broken brake lines.
Rear wheels lock up under normal braking
- Tires are over-inflated.
- Excessively worn protectors.
Rear wheels lock up during emergency braking
- Tires are over-inflated.
- The protectors are worn too much.
- The brake pads of the front wheels are contaminated with oil.
- Faulty GTZ, or assembly (And) brake mechanisms.
The parking brake does not hold the vehicle properly
- The adjustment of the parking brake drive is broken.
Suspension and steering fault diagnosis
Note. Before testing suspension and steering components, verify that the problem is not caused by improper tire inflation, mismatched tire sizes, wheel imbalance, or «tacking» brakes.
Violated directional stability of the car
- Wheels of different sizes are installed on one axle, or their tires are inflated with different pressures.
- Tires are defective.
- Worn suspension or steering components.
- The adjustment of the angles of installation of the front wheels is broken.
- «tacked on» front wheel brakes.
- The wheel bearing preload is out of adjustment.
- broken or «sank» coil springs (with appropriate vehicle equipment).
- Loose wheel nuts.
- The geometry of the suspension or steering gear is broken as a result of an accident.
There is wheel play and increased vehicle vibration
- Front wheel imbalance (vibration is transmitted most noticeably through the steering wheel).
- Rear wheel imbalance (vibration is transmitted most noticeably through the body of the car).
- Tires are unevenly inflated.
- The wheel bearing preload is out of adjustment.
- Worn suspension strut components.
- Loose wheel nuts.
- Damaged or deformed wheels.
- Tires damaged.
- Worn steering or suspension components, or their ball joints and/or rubber bushings.
- Worn ball joint (s).
During cornering and braking, «galloping» and/or vehicle rocking
- The anti-roll bar has loosened.
- Shock absorbers faulty.
- broken or «sank» coil springs / suspension springs.
- Worn steering or suspension components, or their ball joints and/or rubber bushings.
- The car is overloaded.
There is yaw or general vehicle yaw
- Wheels of different sizes are installed on one axle, or their tires are inflated with different pressures.
- Wheel balance out of alignment.
- Tires unevenly inflated.
- Loose wheel nuts.
- There is a lack of lubrication of CV joints and tie rod ends.
- Worn shock absorbers.
- The anti-roll bar has loosened.
- broken or «sank» coil springs/springs.
- The adjustment of the angles of installation of the front wheels is broken.
- Worn steering or suspension components, or their ball joints and/or rubber bushings.
Steering wheel too hard to turn
- The fluid level of the power steering system has dropped.
- Tires incorrectly inflated.
- There is a lack of lubrication of ball bearings and tie rod ends.
- The adjustment of the angles of installation of the front wheels is broken.
- The steering mechanism is out of adjustment, or the lubrication level has dropped.
- The wheel bearing preload is out of adjustment.
- Worn or damaged steering components.
- The rotation of the steering shaft is hindered by the turn signal switch.
- Tires are too lightly inflated.
- The lubricant has deteriorated. Replace.
- Worn or damaged ball joints.
- Worn or damaged steering components.
Excessive steering wheel play
- Loose wheel bearings.
- Worn bushings of suspension components.
- Steering gear out of alignment.
- The adjustment of the angles of installation of the front wheels is broken.
- Loose steering gear assembly.
- Worn steering or suspension components.
No hydraulic boost
- The steering pump drive belt is damaged, or its tension adjustment is broken.
- The hydraulic fluid level has dropped.
- The patency of the power steering system hoses is broken.
- Air has entered the hydraulic path of the power steering system.
- Steering pump defective.
- Steering gear defective.
Serviceability of return of a steering wheel in a straight line position is broken
- The adjustment of the angles of installation of the front wheels is broken.
- Tires are too lightly inflated.
- Worn steering components.
- Steering column adjustment is broken.
- Worn or damaged ball joints.
- Worn or damaged steering components.
- Steering gear components have lost lubrication.
- The level of lubrication in the crankcase of the steering mechanism has fallen.
- Steering column jammed.
The steering wheel rotates in different directions with different resistance
- There are leaks in the steering gear case.
- The patency of the hydraulic lines of the power steering system is broken.
Steering pump is noisy
- There is a lack of oil in the pump.
- The patency of the hoses or the steering pump oil filter is broken.
- Loose drive pulley.
- The adjustment of the tension force of the steering pump drive belt is broken.
- Steering pump defective.
There are extraneous noises coming from the front of the car
- Tires incorrectly inflated.
- There has been a loss of lubrication of the ball joints or steering gear components.
- Loose steering gear, steering and suspension components.
- Worn shock absorber mounts.
- Dampers damaged.
- Springs damaged.
- Loose wheel nuts.
- Worn or damaged rear axle splines.
- Excessive axial play of the rear axle.
Decreased vehicle control during braking
- Worn front wheel bearings.
- broken or «sank» coil springs / suspension springs.
- Warped brake discs/drums.
The car sank excessively
- Overload
- Shock absorbers worn out rack assemblies.
- broken or «sank» coil springs / suspension springs.
- Serviceability of functioning of an electropneumatic suspension bracket is broken (with appropriate equipment).
There is a grinding or other extraneous noise emitted by the steering mechanism
- Loose rack and pinion assembly fasteners.
- There is internal damage to the steering gear.
Excessive tire wear
Increased wear on the inside or outside of the tread
- Tires under-inflated (wear on both ends).
- The adjustment of the angles of installation of the front wheels is broken.
- Worn steering or suspension components, or their ball joints and/or rubber bushings.
- No speed reduction when cornering.
- There is a mechanical violation of the geometry of the suspension as a result of the accident.
Scale wear (fraying) protector
- Convergence setting violated.
Wear of the central part of the tread
- Tires are over-inflated.
Wear on the inner and outer edges of the tread
- Tires under-inflated.
- Worn shock absorbers.
Uneven tread wear
- Tire/wheel out of balance.
- Excessive wheel or tire lateral runout.
- Worn shock absorbers.
- Tire damaged.