Mounting locations for units of a typical emission control system on a 2.7 L 4-cylinder engine
1. Recirculation valve; 2. Vacuum valve controlling the recirculation valve; 3. Vacuum distributor controlling the recirculation valve; 4. Converter; 5. Oxygen sensor; 6. Control valve; 7. Tank with gasoline vapor absorber; 8. Vacuum distributor controlling the reservoir valve
Vacuum hoses on 3.4L V6 engine
1. Crankcase ventilation spool; 2. Recirculation valve; 3. Vacuum valve controlling the recirculation valve; 4. Vacuum distributor controlling the recirculation valve; 5. Gasoline vapor sensor; 6. Control valve; 7. Vacuum distributor controlling the reservoir valve; 8. Tank with gasoline vapor absorber; 9. Oxygen sensor 2
The vehicles covered in this manual are equipped with several emission control systems. The specific design of the environmental protection system is determined by the brand of the car and the territory of its sale. These systems include:
- forced crankcase ventilation system (PCV system),
- gasoline vapor recovery system (EEC system),
- exhaust gas recirculation system (EGR system),
- catalytic converter (TWC),
- pulsating system of after-oxidation of exhaust gases (PAIR system).
- onboard diagnostic system (OBDII system).
The specific type of systems indicating the adjustment data and the wiring of the vacuum hoses is indicated on the engine compartment plate (VECI plate).
Failure of sensors and devices of some emission control systems can affect engine performance. Reading diagnostic codes and pinpointing a specific faulty device is possible thanks to the use of an OBDII on-board diagnostic system on the vehicle (since 1996). To read diagnostic trouble codes in this system and identify them, special expensive scanners are required, so it is advisable to perform all types of diagnostic, repair and adjustment work in a car service.