Heated Oxygen Sensor (H02S)

When the ignition is turned to position III (crank,) the ECM communicates with the alarm ECU. If it receives authority to start, the ECM begins ignition and fuelling when CKP and CMP sensor signals are detected. The ECM will run the fuel pump continuously when CKP sensor signals are received (crank turning). When the ignition switch is turned to position 0 (off), the ECM switches off ignition and fuelling to stop the engine. The ECM continues to hold the main relay in the on position until it has completed the power down functions. Power down functions include engine cooling and referencing the IAC valve stepper motor and includes memorising data required for the next start up. When the power down process is completed, the ECM switches off the main relay and enters a low power mode. During low power mode the ECM will consume less than 1mA.

If the ECM suffers an internal failure, such as a break down of the processor or driver circuits, there are no back up systems or limp home capability. If a sensor circuit fails to supply an input, this will result in a substitute or default value being adopted where possible. This enables the vehicle to function, but with reduced performance.

Heated Oxygen Sensor (H02S)

A H0₂S is located upstream of the catalytic converter, in the exhaust manifold (up to 2001 MY) or the twin pipe section of the exhaust front pipe (from 2001 MY). From 2001 MY, a HO₂S is also installed in the downstream side of the catalytic converter. The upstream HO₂S provides a feedback signal to the ECM to enable closed loop fuelling control. Where fitted, the downstream HO₂S provides a feedback signal to enable the ECM to monitor the efficiency of the catalytic converter, by comparing the signals from the upstream and downstream HO₂S.

If the upstream H0₂S fails, the ECM adopts an open loop fuelling strategy. If the downstream HO₂S fails, the ECM suspends catalytic converter monitoring.

A. Ambient Air. B. Exhaust Gases.

1. Protective ceramic coating.
2. Electrodes.
3. Zirconium Oxide.

CAUTION: H0₂ sensors are easily damaged by dropping, excessive heat or contamination. Care must be taken not to damage the sensor housing or tip. • The H0₂S becomes very hot, take care when working near it. • Do not measure the resistance of the sensing element. • Observe the correct torque tightening value when installing the H0₂S. • Do not subject the H0₂S to mechanical shocks. • The H0₂S may be contaminated if fuel with added lead is used.