P1157

DTC P1157:A/F Sensor (Sensor 1) Circuit Malfunction

1. Reset the ECM/PCM.
2. Start the engine.

Is DTC P1157 indicated?

YES - Go to step 3.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and at the ECM/PCM.

3. Turn the ignition switch OFF.
4. Disconnect the A/F sensor (Sensor 1) 4P connector and ECM/PCM connector A (31 P).




5. Connect the A/F sensor (Sensor 1) 4P connector terminals No.1 and No.2 with a jumper wire.




6. Check for continuity between ECM/PCM connector terminals A6 and A16.

Is there continuity?

YES - Go to step 9.

NO - Go to step 7.




7. Connect the A/F sensor (Sensor 1) 4P connector terminal No.1 to body ground with a jumper wire.




8. Check for continuity between ECM/PCM connector terminal A6 and body ground.

Is there continuity?

YES - Repair open in the wire between the A/F sensor (Sensor 1) and the ECM/PCM (A16).

NO - Repair open in the wire between the A/F sensor (Sensor 1) and the ECM/PCM (A6).

9. Substitute a known-good A/F sensor (Sensor 1) and recheck.

Is DTC P1157 indicated?

YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM,then recheck. if the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Replace the A/F sensor (Sensor 1).