Engine management system - MEMS (Diagnostic connector): Description and operation

Diagnostic connector

A diagnostic connector, located on a bracket above the passenger compartment fuse box, allows engine tuning or fault diagnosis to be carried out using TestBook without disconnecting the ECM harness multiplug.

Heated oxygen sensor

The modular engine management system operates a closed loop emission system to ensure the most efficient level of exhaust gas conversion.

A heated oxygen sensor (HO2S) fitted in the exhaust manifold monitors the exhaust gases. It supplies a small voltage proportional to exhaust oxygen content to the ECM. As the air/fuel mixture weakens, the exhaust oxygen content increases and the voltage to the ECM decreases. If the mixture becomes richer, the oxygen content decreases and the voltage to the ECM increases.

From this signal the ECM can determine the air/fuel mixture being delivered to the engine and can adjust the duration the injectors are open to maintain the ratio necessary for efficient gas conversion by the catalyst.

The HO2S has an integral heating element to ensure an efficient operating temperature is quickly reached from cold. The electrical supply to the heater element is controlled by the ECM via the HO2S relay in the relay module.