DTC Troubleshooting: P1157 (48-5)

DTC P1157 (48-5):  A/F Sensor (Sensor 1) Circuit Malfunction


1.Reset the ECM/PCM.

2.Start the engine.

Is DTC P1157 indicated?


YES - Go to 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.n


3.Turn the ignition switch OFF.

4.Disconnect the A/F sensor (Sensor 1) 4P connector and ECM/PCM connector A (31P).

5.Connect 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 9.


NO - Go to 7.


7.Connect 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).n


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


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.n


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