Note. Below is a brief description of the purpose, operation and location of each of the important information sensors. Sensor names use standard terminology recommended by the Society of Automotive Engineers (SAE). Where Toyota uses other names (for some sensors), also given the name by Toyota.
6. Accelerator pedal position sensor (APP) All 2004 and later models covered in this manual are equipped with Intelligent Electronic Throttle Control (ETCS-i). This system dispenses with the conventional cable-operated accelerator and uses an electrically actuated throttle instead of the conventional cable-operated throttle. Powertrain control module (RSM) controls the throttle position with an electromagnet located in the throttle body. The PCM commands are based on the input signals it receives from the APP sensor. The sensor is located on top of the accelerator pedal assembly. Its electrical output signal, which is proportional to the angle of the accelerator pedal, is used by the ETCS-i system to determine the corresponding opening angle of the throttle valve located inside the corresponding housing.
7. Camshaft position sensor (SMR) - The CMP sensor monitors the position of the camshaft and tells the powertrain control module when the piston in cylinder #1 is not in the compression stroke. The PCM uses the signal from the CMP sensor to set the firing order of the fuel injectors. Four-cylinder engines have one CMP sensor. It is located on the left end of the cylinder head, near the left end of the intake camshaft. V6 engines have two CMP sensors, one for each cylinder head. They are located on the left end of the cylinder heads, near the left end of each intake camshaft. On V6 engines, according to Lexus and Toyota terminology, CMP sensors are called WT sensors. For more information on intelligent variable gas distribution system (WT-i) talk to paragraph 19.
The CMP sensor is a variable magnetic resistance sensor (inductive type). It generates an analog pulse signal (sinusoidal), when each of the protrusions on the impulse wheel passes the sensor. On four-cylinder engines, the impulse wheel is mounted on the left end of the intake camshaft. On V6 engines, the impulse wheels are located on the underside of the WT-i controllers, which are mounted on the left end of each intake camshaft. There are three lugs on each impulse wheel. As the impulse wheel rotates with the camshaft, the CMP sensor generates an output voltage each time one of the protrusions on the impulse wheel passes the sensor. The intake camshaft makes one revolution for every two revolutions of the crankshaft. Therefore, there are three voltage outputs for every two revolutions of the crankshaft. The PCM uses these output signals to determine the position of the intake camshaft.
8. Crankshaft position sensor (TFR) - Like the CMP sensor, the SKR sensor is a variable magnetic resistance sensor (inductive type), which generates an analog pulse signal (sinusoidal), when each of the protrusions on the impulse wheel passes the sensor. On four-cylinder engines, the TFR sensor is located on the front side of the timing chain cover, next to the crankshaft pulley/damper. The impulse wheel is mounted on the front end of the crankshaft in front of the sprocket. On V6 engines, the TFR sensor is located on the front side of the engine, next to the crankshaft pulley/damper, and the impulse wheel is mounted on the crankshaft at the rear of the timing belt sprocket. Each impulse wheel has 36 evenly spaced teeth, with two teeth missing. That is, in fact, there are 34 teeth, and instead of the other two, there are empty openings. As the crankshaft rotates, each tooth on the impulse wheel passes in front of the TFR sensor. As each tooth passes in front of the sensor, the magnetic flux in the sensor coil changes because the air gap between the sensor and the impulse wheel changes. This change in magnetic flux initiates a voltage pulse in the sensor, and this pulse is sent to the PCM as an output signal. Empty holes where missing teeth are used by PCM to determine top dead center (TDC).
The CKP sensor is the main sensor that provides ignition information to the PCM. The PCM uses a CKP sensor to determine the position of the crankshaft (Which piston will be next at TDC?) and engine speed (rpm). Both of these parameters are needed to set the order of operation of the ignition system.
9. Engine coolant temperature sensor (EATING) — The ECT sensor measures the engine coolant temperature. It is a thermistor, that is, its resistance decreases with increasing temperature and increases with decreasing temperature. This type of thermistor is also referred to as NTC thermistor (NTC). This variable resistor causes an analog voltage drop across the sensor terminals, resulting in an electrical signal to the PCM that accurately reflects the engine coolant temperature.
The ECT sensor is an important sensor because it tells the PCM when the engine is warm enough to enter closed loop operation. Once the engine starts in closed loop mode, the PCM uses the ECT sensor to also control the fuel injector pulse width and ignition timing. It also uses the ECT sensor signal to determine when to purge the EVAP system.
On four-cylinder engines, the ECT sensor is located at the left end of the cylinder head (on the driver's side). On V6 models, the ECT sensor is located on the right end of the engine (where is the timing belt located), on the coolant distribution housing.
10. Air intake temperature sensor (IAT) - The IAT sensor is used by the PCM to calculate the air density, which is one of the parameters that the module needs to know in order to calculate the injector pulse width and adjust the ignition timing (to prevent detonation at high air intake temperatures). Like the ECT sensor, the IAT sensor is an NTC thermistor (NTC), whose resistance decreases with increasing temperature. The IAT sensor is an integral part of the mass air flow sensor (MAF), located on the air filter housing. For more information about the MAF sensor, refer to paragraph 12.
11. Knock Sensor - The knock sensor monitors engine vibration caused by knocking. Typically, a knock sensor converts engine vibration into an electrical signal. When the knock sensor detects knocking in one of the cylinders, it sends a signal to the PCM, not so that the PCM can advance the ignition accordingly. The knock sensor contains a piezoelectric material (a certain type of piezocrystal), which has the ability to generate voltage when mechanical stress occurs in it. The piezoelectric crystal in the knock sensor constantly vibrates and generates an output signal proportional to the intensity of the vibration. As the vibration intensity increases, the output voltage changes accordingly. When the vibration intensity of the crystal reaches a predetermined threshold, the PCM stores this value in memory and advances the ignition in all cylinders (PCM cannot advance selectively, i.e. only in the problem cylinder). The PCM does not respond to knock sensor input when the engine is idling. It only reacts when the engine reaches the prescribed speed.
On four-cylinder engines, the knock sensor is located on the underside of the cylinder block, below the exhaust manifold passages. To gain access to it, the intake manifold must be removed. On V6 engines, knock sensors (two pieces) located in the opening between the cylinder heads. On these models, the upper and lower sections of the intake manifolds must be removed to access the knock sensors.
12. Mass Air Flow/Intake Temperature Sensor (MAF/IAT) - The MAF sensor is the main device by which the PCM monitors intake air flow. It uses a sensitive element, made in the form of a wire heated to a high temperature, which allows you to measure the amount of air entering the engine. Air flowing around a heated piece of wire causes it to cool. The temperature of the sensing element is maintained at 200°C above the outside temperature by passing an electric current through the wire, the whole process being controlled by the PCM. Constantly «cold» wire, two placed to the right of «hot» wire, measures the temperature of the outdoor air. When the intake air passes through the MAF sensor and flows around «hot» wire, it cools this wire and the control system immediately corrects the temperature, bringing it to the set value. The current required to maintain the set temperature constant is used by the PCM as an indication of the airflow.
On all models, the function of the MAF sensor and the air intake temperature sensor (IAT) merged into one node. For more information about the IAT sensor, see L. 10. The MAF/IAT sensor is located on top of the air filter housing.
13. Oxygen sensors - Oxygen sensors generate a voltage signal that varies according to the amount of oxygen in the exhaust stream. The PCM uses data from the front oxygen sensor to calculate the pulse width of the injectors. The rear oxygen sensor monitors the oxygen content in the exhaust gases leaving the catalytic converters. This information is used by the PCM to predict deterioration and/or failure of the catalytic converters. One of the tasks of a catalytic converter is to store excess oxygen. As long as the catalytic converter is working properly, the rear sensor should show little activity because there should be little oxygen leaving the catalytic converter. But as the catalytic converter «produced», its ability to store oxygen deteriorates. When the output from the rear sensor becomes similar to the output from the front sensor, the PCM generates a DTC and illuminates the MIL, indicating to the driver that it is time to replace the catalytic converter.
On models 2001-2003. With a four-cylinder engine, there are four oxygen sensors: one front and one rear sensor for each three-way catalytic converter (WU-TWC). On these models, both three-way catalytic converters are an integral part of the respective exhaust manifold. 2004 and later models with a four-cylinder engine have only one three-way catalytic converter (it is also an integral part of the exhaust manifold). Therefore, on these models there are only two sensors - one in front of the converter (front) and one after him (rear).
V6 models have four oxygen sensors: one in each exhaust manifold, ahead of the three-way catalytic converter (WU-TWC), and one in each downpipe, between the three way converter and the rear catalytic converter.
14. Power steering pressure sensor (PSP) - The PSP sensor monitors the pressure of the working fluid in the power steering system. The PSP sends an input signal to the PCM, the voltage of which changes according to changes in hydraulic pressure. The PCM uses input from the PSP sensor to increase idle speed when the engine is already under some other load, such as from an A/C compressor, when maneuvering the vehicle at low speed (when parking) or driving in «stop-start». The PSP sensor also signals the PCM to adjust the injector air solenoid valve in situations where there is a high load, such as when parking. The PSP sensor is located in the power steering pump. On models with a four-cylinder engine, it is screwed directly into the pump. On models with a V6 engine, it is screwed from above into the union bolt type «banjo», used to connect the power steering pressure hose to the pump.
15. Throttle position sensor (TR) - The TP sensor, which is located on the throttle body, is a rotary potentiometer. Basically it's a resistor (variable resistor), which generates a signal whose voltage changes in proportion to the throttle opening angle. The PCM sends a 5V reference voltage to the TP sensor. As the damper opens and closes, the resistance of the TP sensor changes, causing a change in the signal sent to the PCM. The output voltage of the TP sensor is in the range of approximately 0.6 V at idle (with closed throttle) up to 4.5 V at wide open throttle. This variable signal enables the PCM to calculate the position (opening angle) throttle valve. The PCM uses the TP sensor input along with inputs from other sensors to adjust the fuel injector pulse width and ignition timing.
The TP sensor is not used on all 1999-2003 models. Not these models, you can replace the TP sensor yourself. All 2004 and later models feature intelligent electronic throttle control (ETCS-i). On models with this system, the TP sensor is an integral part of the electronic throttle body and cannot be serviced separately from the throttle body.
16. Transmission range sensor (TR) - TR sensor similar to park/neutral position switch (PNP), which it replaces, prevents the engine from starting unless the automatic transaxle is in park gear (R) or neutral (N). In addition, it turns on the reversing lights when the selector lever is moved to the reverse gear position (R). Unlike the PNP switch or the starter lock switch, the TR sensor also tells the PCM what gear the gearbox is in. The PCM uses this information to determine engine load, engine speed, vehicle speed, etc. based on data. determine which gear should be engaged in the gearbox, as well as in order to determine when it is necessary to perform upshifts and downshifts. The TR sensor is not installed on the front side of the transmission.
17. Transmission Speed Sensors - All Transmissions (in block with drive axle) two speed sensors are installed: a turbine input speed sensor or an input shaft speed sensor and an intermediate gear speed sensor. These sensors are variable reluctance sensors (inductive type), which generate an analog pulse signal (sinusoidal form) each time you pass the ledge on the impulse wheel in front of the sensor. Both sensors are located on top of the gearbox. The PCM uses the signal from the turbine input speed sensor to monitor the turbine inlet speed or input shaft speed. The signal from the intermediate gear speed sensor is used to monitor the intermediate gear speed or output shaft speed. The PCM constantly compares both speeds with the characteristic (programmed) values for the gearbox to determine the order of gear shifting, the order of engagement of the torque converter clutch (TSS) and optimal hydraulic pressure for various hydraulically controlled elements located inside the gearbox. Both sensors are located on top of the gearbox. The turbine input speed sensor is an item located on the left (on the driver's side) the end of the gearbox; the intermediate gear speed sensor is located to the right of the turbine input speed sensor, closer to the protruding front section of the crankcase.
18. Vapor pressure sensor - The vapor pressure sensor is an element of the fuel vapor recovery system (EVAP), it is located on top of the fuel tank. The vapor pressure sensor monitors the vapor pressure of the fuel inside the tank. When the vapor pressure exceeds the upper threshold, the vapor pressure sensor sends a signal to the PCM, which opens the vacuum switching valve (VSV) for the pressure switch valve, allowing fuel vapor to go to the EVAP canister where it is stored until purged.