VIN Range: N52207->N99999

Engine Emission Control - VIN Range: N52207->N99999

Positive Crankcase Ventilation (PCV) System
The PCV system recycles crankcase gases back through the engine where they mix with incoming air/fuel charge and help to reduce hydrocarbon emissions.

Vehicles with 3.0L engine
The PCV system consists of two hoses, connected between the left-hand valve cover and the intake manifold and the right-hand valve cover and the air cleaner outlet pipe.

Vehicles with 4.2L engine
The PCV system consists of a valve, and two hoses. The PCV valve is mounted on the right-hand valve cover and a hose is connected between PCV valve and the throttle body elbow. The left-hand valve cover PCV hose is connected to the air cleaner outlet pipe.

The PCV valve regulates the amount of ventilation air and crankcase gas supplied to the intake manifold and also prevents backfiring into the crankcase.

Exhaust Gas Recirculation (EGR) System - Vehicles with 4.2L engine

EGR Valve







EGR Valve Tube







The EGR system comprises of an EGR valve and exhaust manifold to EGR valve tube. The EGR system allows a measured quantity of exhaust gas to be directed back to the intake manifold. The exhaust gas is introduced to the incoming charge air in the intake manifold, where it mixes with the air/fuel mixture and lowers the peak gas temperature, reducing nitrogen oxide (NOx) exhaust emissions. The gas is drawn through the exhaust manifold to EGR valve tube from the exhaust to the inlet manifold through the EGR valve. The EGR valve is electrically operated and is controlled through an input from the engine control module (ECM).

On vehicles without a supercharger the EGR valve is mounted on the intake manifold. On vehicles with a supercharger the EGR valve is mounted on the throttle body elbow.

The ECM monitors the operation of the EGR system from inputs from the manifold absolute pressure (MAP) sensor and can detect high or low flow through the valve as a result of changes to the pressure readings.

High or low flow outside the expected range results in the setting of a diagnostic trouble code (DTC).

On vehicles without a supercharger the MAP sensor is mounted on the rear of intake manifold. On vehicles with a supercharger the MAP sensor is mounted on the rear of the throttle body elbow.

Secondary Air Injection (AIR) System







To assist in the reduction of exhaust emissions to meet European Union (EU) Stage 4 and Federal Petrol Emission standards, AIR is fitted to the vehicle.

The AIR pump is used to provide a supply of air into the exhaust manifolds during the cold start period of the engine. The AIR cycle lasts for up to 65 seconds. The hot unburnt fuel particles leaving the combustion chamber mix with the air injected into the exhaust manifolds and immediately combust.

This subsequent combustion of the unburnt and partially burnt carbon monoxide (CO) and hydrocarbon (HC) particles help to reduce the emission of these pollutants from the exhaust system. The additional heat generated in the exhaust manifold also provides rapid heating of the exhaust system catalytic converters. The additional oxygen which is delivered to the catalytic converters also generates an exothermic reaction which causes the catalytic converters to reach their optimum operating temperature and 'light off' quickly.

The catalytic converters only start to provide effective treatment of emission pollutants when they reach an operating temperature of approximately 250 degree C (482 degree F) and need to be between temperatures of 400 degree C (752 degree F) and 800 degree C (1472 degree F) for optimum efficiency. Consequently, the heat produced by the AIR 'afterburning' reduces the time delay before the catalysts reach an efficient operating temperature.

The AIR system comprises the following components:
- AIR pump
- AIR switching valve
- AIR control valve
- AIR vacuum reservoir
- AIR pump relay
- AIR pressure sensor (North American specification vehicles only)

AIR Pump







The AIR pump is located behind the left-hand side of the front bumper cover. The pump is fitted on rubber mountings to help prevent noise which is generated by AIR pump operation. The AIR pump is powered from the vehicle battery by a dedicated relay and supplies approximately 10 to 15 kg/hr (22 to 33 lb/hr) of air when the engine is at idle speed and the ambient temperature is below 20 degree C (68 degree F).

Air is drawn into the AIR pump through vents in its front cover and is then passed through a foam filter. The air is delivered to the exhaust manifold on each side of the engine through a combination of plastic pipes and stainless steel tubes.

One second after the AIR pump is energized, the ECM switches on the AIR switching valve, which opens to allow vacuum from the AIR vacuum reservoir to be applied to the vacuum operated AIR control valve. When the vacuum is applied to the AIR control valve, it opens to allow the air from the AIR pump through to the exhaust manifolds.

When the ECM switches off the AIR switching valve, the vacuum supply to the AIR control valve is cut-off and the valve closes to prevent further air being injected into the exhaust manifolds. With an approximate five second delay after as the AIR switching valve is closed, the ECM removes power from the AIR pump relay, and this in turn stops the AIR pump from operating.

AIR Switching Valve







The ECM switches on the AIR switching valve with a one second delay after initiating AIR pump operation. When the AIR switching valve is open, a steady vacuum supply is allowed through to open the vacuum operated AIR control valve. When the ECM switches off the AIR switching valve, the valve closes and immediately shuts off the vacuum supply to the AIR control valve. The pump continues to operate for a further five seconds for system diagnostic purposes.

When the AIR switching valve is switched off, the vacuum supply line opens to atmosphere, and this causes the AIR switching valve to close automatically to prevent any further injection of air.

AIR Control Valve







The injected air from the AIR pump is controlled by the AIR control valve. This allows the correct amount of air to be injected directly into the exhaust manifolds. The AIR control valve prevents exhaust gasses from blowing back into the AIR pump.

The AIR control valve is assisted in operation by a vacuum source from the AIR vacuum reservoir located in the right-hand side of the engine bay. This assistance allows the actuation of the AIR control valve independently from the intake manifold vacuum levels available.

When the pressure in the exhaust system is higher than in the AIR system, the AIR control valve closes the circuit, and this protects the AIR system from exhaust gasses blowing back into the AIR system.

Vacuum to the AIR switching valve is provided from the intake manifold vacuum by the AIR vacuum reservoir. A small bore vacuum hose provides the vacuum route between the AIR vacuum reservoir and AIR switching valve. A further small bore vacuum hose is used to connect the AIR switching valve to the AIR control valve.

AIR Vacuum Reservoir







The AIR vacuum reservoir is located on the right-hand side of the engine bay.

The AIR vacuum reservoir is included in the vacuum supply line between the intake manifold and the AIR switching valve.

The AIR vacuum reservoir contains a one-way valve to stop vacuum leaking back towards the intake manifold side. The AIR vacuum reservoir holds a constant vacuum so that the AIR control valve opens as soon as the AIR switching valve is switched on.

AIR Pump Relay
The AIR pump relay is located in the engine compartment fusebox. The ECM is used to control the operation of the AIR pump by the AIR pump relay.

The AIR system receives its voltage supply through the AIR pump relay. The ECM monitors the state of the relay for correct operation as part of its system diagnostic.

AIR Pressure Sensor - North American specification vehicles only
The AIR system is monitored by measuring the system pressure by using the AIR pressure sensor at several instances during its cycle of operation.

The AIR system pressure is measured before operation of the AIR pump. The AIR pump is then switched on and with a one second delay, the AIR switching valve is opened. After a stabilizing period, the system pressure is measured again, this time by taking the average of a one second duration of readings, and normalising for variations in battery voltage and atmospheric pressure. If the system pressure measured at this time has not risen enough with respect to the initial AIR pressure reading then a failure will be flagged.

A second pressure measurement is made after the requirement for AIR into the exhaust system has expired, but continuing on from the same period of AIR pump operation, i.e. the pump is left running, against a closed AIR switching valve. Again this pressure measurement is the average of a one second duration of readings normalised for variations in battery voltage and atmospheric pressure. If the system pressure measured at this time has not risen enough or has risen too much with respect to the system pressure during normal operation of AIR then a failure will be flagged.

A final pressure reading is taken after the AIR system has been switched off to ensure the system shuts down.