Emission control system

EMISSION CONTROL SYSTEM

Catalytic Converter System

Heated Oxygen sensor The heated oxygen sensor is mounted in the exhaust front pipe close to the manifold. It is formed by three insulated platinum coated elements inside a protective tube. The elements are brought together at the sensing tip and form an electrode sensitive to Oxygen.

A 12v feed is supplied from the oxygen sensor relay on a N/U wire, to the input element of the sensor which supplies the heater coil and the sensing tip. The heater coil surrounds the sensing tip to ensure an efficient operating temperature is quickly reached from cold. The heater coil operates continually and is earthed through the B wire.

In weak air/fuel mixtures, heated oxygen content in the exhaust gas increases and the build up of oxygen reduces the resistance of the sensing tip. As the air/fuel mixture becomes richer so oxygen content decreases, resistance of the sensing tip is increased and so current flow decreases.

The resultant voltage difference is transmitted on the LG/S and S wires to the ECM which can then determine whether any correction to fuel delivery is necessary.

CAUTION: A heated oxygen sensor will not operate if its power supply is removed, if it has been dropped or subjected to any impact or if cleaning materials are used on it.

Purge Valve

The ECM controls the operation of the purge valve on the Y/O wire. The valve remains closed when the engine is cold and at idling speed to protect engine tune and catalyst performance. When the coolant is above 70C, the purge valve solenoid will be modulated ON and OFF whenever the engine speed is above 1500 rev/min and the manifold absolute pressure is below 30kpa. When the purge valve is open fuel vapour from the charcoal canister is drawn into the throttle housing for combustion.