DTC Troubleshooting: P0135 (41-2)

DTC P0135 (41-2):  Primary HO2S (Sensor 1) Heater Circuit Malfunction

1.Reset the ECM/PCM.

2.Start the engine.

Is DTC P0135 indicated?


YES - Go to 3.


NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the ECM/ PCM.n


3.Turn the ignition switch OFF.

4.Disconnect the primary HO2S (Sensor 1) 4P connector.

5.At the primary HO2S side, measure resistance between the primary HO2S (sensor 1) 4P connector terminals No. 3 and No. 4.

 

Is there about 6 W (at room temperature)?


YES - Go to 6.


NO - Replace the  primary HO2S (Sensor 1).n

6.Check for continuity between body ground and the primary HO2S (Sensor 1) 4P connector terminals No. 3 and No. 4 individually.

 

Is there continuity?


YES - Replace the  primary HO2S (Sensor 1).n


NO - Go to 7.


7.Turn the ignition switch ON (II).

8.Measure voltage between the primary HO2S (Sensor 1) 4P connector terminal No. 3 and No. 4.

 

Is there battery voltage?


YES - Go to 9.


NO - Go to 12.


9.Turn the ignition switch OFF.

10.Disconnect ECM/PCM connector A (31P).

11.Check for continuity between ECM/PCM connector terminal A1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the ECM/PCM (A1) and the primary HO2S (Sensor 1).n


NO - 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


12.Measure voltage between the primary HO2S (Sensor 1) 4P connector terminal No. 3 and body ground.

 

Is there battery voltage?


YES - Go to 13.


NO - Check the No. 3 (7.5A) fuse in the under-dash fuse/relay box. If the fuse is OK, repair open in the wire between the primary HO2S (Sensor 1) and No. 3 (7.5A) fuse.n

13.Turn the ignition switch OFF.

14.Reconnect the primary HO2S (Sensor 1) 4P connector.

15.Disconnect ECM/PCM connector A (31P).

16.Turn the ignition switch ON (II).

17.Measure voltage between ECM/PCM connector terminal A1 and A5.

 

Is there 0.1 V or less?


YES - Repair open in the wire between the ECM/PCM (A1) and the primary HO2S (Sensor 1).n


NO - 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