P0135

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

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

Is DTC P0135 indicated?

YES - Go to step 3.

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

3. Turn the ignition switch OFF.
4. Disconnect the primary HO2S (Sensor 1) 4P connector.




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

Is there 3.0 - 3.6 Ohms at room temperature?

YES - Go to step 6

NO - Replace the primary HO2S (Sensor 1).




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

Is there continuity?

YES - Replace the primary HO2S (Sensor 1).

NO - Go to step 7.

7. Turn the ignition switch ON (II).




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

Is there battery voltage?

YES - Go to step 9.

NO - Go to step 12.

9. Turn the ignition switch OFF.
10. Disconnect PCM connector A (31P).




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

Is there continuity?

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

NO - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.




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

Is there battery voltage?

YES - Go to step 13.

NO - Check the No.4 ACG (10A) 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.4 ACG (10A) fuse.

13. Turn the ignition switch OFF.
14. Reconnect the primary HO2S (Sensor 1) 4P connector.
15. Disconnect PCM connector A (31P).
16. Turn the ignition switch ON (II).




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

Is there 0.1 V or less?

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

NO - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM. replace the original PCM.