P042
DTC P042:
Oxygen Sensor Circuit:
CIRCUIT DESCRIPTION:
The PCM provides a 0.45 volt reference signal to the oxygen sensor on CKT 412. When the oxygen sensor is cold (below 2000°C), the oxygen sensor signa voltage will be around 0.45 volt and the PCM will keep the system is open loop operation. When the oxygen sensor is warm (above 2000°C), the oxygen sensor will swing from rich to lean rapidly, at least one swing every two seconds, if the PCM is in good control of the air fuel mixture. Code P042 is designed so that if the oxygen sensor stays at a lean voltage for more than 50 seconds during the test conditions, Code P042 will set. Code P042 will set when:
1. There is an oxygen sensor circuit fault giving a false lean indication.
OR
2. When the air fuel ratio is actually lean due to a vacuum leak or fuel control system fault.
TEST CONDITION(S):
1. Codes P014, P015, P016, P021, P022, P026, P027, P031, P032, and P034 not set.
2. Throttle position switch open.
3. If Sensor between 5.4 and 25.
4. Coolant temperature between 81.5°C and 131°C.
5. Oxygen sensor ready.
6. Engine speed 800 rpm or greater.
7. Low coolant level and engine overheat not present.
8. Traction control not active.
9. MAP sensor greater than 20.2 kPa.
10. Evaporative Emission (EVAP) Canister Purge on full with TP sensor greater than 100.
11. Long term fuel trim not in effect.
FAILURE CONDITION(S):
Oxygen sensor remains lean (356 mV (0.356V) or less) for more than 50 seconds.
ACTION TAKEN:
1. PCM turns "ON" the "SERVICE ENGINE SOON" MIL.
2. PCM enables evaporative emission control solenoid if Code P044 is also set.
3. Transaxle shift adapts are maintained at current levels.
NOTES ON FAULT TREE:
1. If Code P017 is also set, diagnose it first because an Oxygen Sensor not ready can cause other emission related problems.
2. If the Oxygen Sensor is operating correctly, voltage will fluctuate above 0.3 volt. A lean sensor/condition will cause the voltage to remain below 0.3 volt.
3. If greater than 0.15 volt is measured, the PCM and CKT 412 are OK.