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DTC P0135: A/F Sensor (Sensor 1) Heater Circuit Malfunction

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  1. Turn the ignition switch to ON (II).
  2. Clear the DTC with the HDS.
  3. Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
  4. Check for Temporary DTCs or DTCs with the HDS.

    Is DTC P0135 indicated? 

    YES  -Go to step 5.

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

  5. Turn the ignition switch to LOCK (0).
  6. Check these fuses:
    • No. 14 OP1 (40 A) fuse in the under-hood fuse/relay box.
    • No. 15 LAF HEATER (20 A) fuse in the under-dash fuse/relay box.

    Are either of the fuses blown? 

    YES  -Repair short in the wire between the A/F sensor relay (LAF) and the fuses. Also replace the blown fuses, then go to step  24.

    NO  -Go to step 7.

  7. Disconnect the A/F sensor (Sensor 1) 4P connector.
  8. At the sensor side, measure the resistance between A/F sensor (Sensor 1) 4P connector terminals No. 3 and No. 4.
    Fig 1: Measuring Resistance Between A/F Sensor (Sensor 1) 4P Connector Terminals No. 3 And No. 4
    G06267367Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 2.1-2.9 Ω at room temperature? 

    YES  -Go to step 9.

    NO  -Go to step  23.

  9. At the sensor side, check for continuity between A/F sensor (Sensor 1) 4P connector terminals No. 2 and No. 3, and No. 2 and No. 4 individually.
    Fig 2: Checking Continuity Between A/F Sensor (Sensor 1) 4P Connector Terminals No. 2, 3 And No. 2, 4
    G06267368Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Go to step  23.

    NO  -Go to step 10.

  10. Jump the SCS line with the HDS.
  11. Disconnect ECM/PCM connector A (31P).
  12. Check for continuity between ECM/PCM connector terminal A10 and body ground.
    Fig 3: Checking Continuity Between ECM/PCM Connector Terminal A10 And Body Ground
    G06267369Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair short in the wire between the ECM/PCM (A10) and the A/F sensor (Sensor 1), then go to step  24.

    NO  -Go to step 13.

  13. Connect A/F sensor (Sensor 1) 4P connector terminal No. 4 to body ground with a jumper wire.
    Fig 4: Connecting A/F Sensor (Sensor 1) 4P Connector Terminal No. 4 To Body Ground With Jumper Wire
    G06267370Courtesy of AMERICAN HONDA MOTOR CO., INC.
  14. Check for continuity between ECM/PCM connector terminal A10 and body ground.
    Fig 5: Checking Continuity Between ECM/PCM Connector Terminal A10 And Body Ground
    G06267371Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Go to step 15.

    NO  -Repair open in the wire between the ECM/PCM (A10) and the A/F sensor (Sensor 1), then go to step  24.

  15. Remove the glove box (see GLOVE BOX REMOVAL/INSTALLATION ).
  16. Remove the A/F sensor relay (LAF) (A).
    Fig 6: Identifying A/F Sensor Relay (LAF)
    G00491760Courtesy of AMERICAN HONDA MOTOR CO., INC.
  17. Connect A/F sensor (Sensor 1) 4P connector terminal No. 3 to body ground with a jumper wire.
    Fig 7: Connecting A/F Sensor (Sensor 1) 4P Connector Terminal No. 3 To Body Ground With Jumper Wire
    G06267373Courtesy of AMERICAN HONDA MOTOR CO., INC.
  18. Check for continuity between A/F sensor relay (LAF) 4P connector terminal No. 1 and body ground.
    Fig 8: Checking Continuity Between A/F Sensor Relay (LAF) 4P Connector Terminal No. 1 And Body Ground
    G06267374Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Go to step 19.

    NO  -Repair open in the wire between the A/F sensor (Sensor 1) and the A/F sensor relay (LAF), then go to step  24.

  19. Disconnect ECM/PCM connector E (31P).
  20. Check for continuity between ECM/PCM connector terminal E8 and body ground.
    Fig 9: Checking Continuity Between ECM/PCM Connector Terminal E8 And Body Ground
    G06267375Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair short in the wire between the ECM/PCM (E8) and the A/F sensor relay (LAF), then go to step  24.

    NO  -Go to step 21.

  21. Check for continuity between ECM/PCM connector terminal E8 and A/F sensor relay (LAF) 4P connector terminal No. 3.

    Is there continuity? 

    Fig 10: Checking Continuity Between ECM/PCM And A/F Sensor Relay (LAF) 4P Connector Terminal
    G06267376Courtesy of AMERICAN HONDA MOTOR CO., INC.

    YES  -Go to step 22.

    NO  -Repair open in the wire between the ECM/PCM (E8) and the A/F sensor relay (LAF), then go to step  24.

  22. Check the A/F sensor relay (LAF) (see POWER RELAY TEST ).

    Is the A/F sensor relay (LAF) OK? 

    YES  -Go to step  30.

    NO  -Replace the A/F sensor relay (LAF), then go to step  24.

  23. Replace the A/F sensor (Sensor 1) (see A/F SENSOR REPLACEMENT ).
  24. Reconnect all connectors.
  25. Turn the ignition switch to ON (II).
  26. Reset the ECM/PCM with the HDS.
  27. Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN PROCEDURE ).
  28. Check for Temporary DTCs or DTCs with the HDS.

    Is DTC P0135 indicated? 

    YES  -Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to step  1.

    NO  -Go to step 29.

  29. Monitor the OBD STATUS for DTC P0135 in the DTCs MENU with the HDS.

    Does the screen indicate PASSED? 

    YES  -Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 28, go to the indicated DTCs troubleshooting.

    NO  -If the screen indicates FAILED, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to step  1. If the screen indicates NOT COMPLETED, keep idling until a result comes on.

  30. Reconnect all connectors.
  31. Update the ECM/PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ).
  32. Start the engine, and let it idle.
  33. Check for Temporary DTCs or DTCs with the HDS.

    Is DTC P0135 indicated? 

    YES  -Check for poor connections or loose terminals at the A/F sensor (Sensor 1), the A/F sensor relay (LAF), and the ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step  32. If the ECM/PCM was substituted, go to step  1.

    NO  -Go to step 34.

  34. Monitor the OBD STATUS for DTC P0135 in the DTCs MENU with the HDS.

    Does the screen indicate PASSED? 

    YES  -If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ). If any other Temporary DTCs or DTCs were indicated in step  32, go to the indicated DTCs troubleshooting.

    NO  -If the screen indicates FAILED, check for poor connections or loose terminals at the A/F sensor (Sensor 1), the A/F sensor relay (LAF), and the ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step  32. If the ECM/PCM was substituted, go to step  1. If the screen indicates NOT COMPLETED, keep idling until a result comes on.

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