Chart A-7 Open Loop Diagnosis

Chart A-7:

Oxygen Sensor Circuit:

DESCRIPTION:

The ECM provides a 0.45 volt reference signal to the oxygen sensor on CKT 412. When the oxygen sensor is cold (below 200°C), the output voltage will be around 0.45 volts and the ECM will keep the system in open loop operation. When warm, a properly operating oxygen sensor will drive the 0.45 volt reference lower (below 0.45 volts) to indicate a lean mixture and higher (above 0.45 volts) to indicate a rich mixture. The oxygen sensor signal voltage will swing from rich to lean rapidly, at least one swing every two seconds, if the ECM is in good control of the air fuel mixture.

NOTES ON FAULT TREE:

1. If a code was not set, the DFI SYSTEM CHECK did not refer to the OXYGEN SENSOR CIRCUIT CHECK UNDER C-CHARTS, which will be required before further diagnosis. If the OXYGEN SENSOR CIRCUIT CHECK indicates a problem, clear codes and road test the vehicle.

2. The code E013 is intermittent and the remainder of the oxygen sensor circuit has passed the OXYGEN SENSOR CIRCUIT CHECK. If none of the above have indicated a problem, the code should be cleared and a road test should be performed.

3. Check for fuel contamination which would result is the failure of the oxygen sensor replace the oxygen sensor and road test the vehicle.