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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 ON (II).
  2. Clear the DTC with the HDS.
  3. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or 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, and the ECM/PCM.

  5. Turn the ignition switch OFF.
  6. Check these fuses:
    • No. 23 LAF (10 A) fuse in the under-dash fuse/relay box.
    • No. 31 LAF (7.5 A) fuse in the under-dash fuse/relay box.

    Are either of the above fuses blown? 

    YES  - Go to step  24.

    NO  - Go to step  7.

  7. Remove the A/F sensor relay (A).
    Fig 1: Identifying A/F Sensor Relay
    G05454501Courtesy of AMERICAN HONDA MOTOR CO., INC.
  8. Check the A/F sensor relay (see POWER RELAY TEST ).

    Is the A/F sensor relay OK? 

    YES  - Go to step  9.

    NO  - Replace the A/F sensor relay, then go to step  33.

  9. Disconnect the A/F sensor (Sensor 1) 4P connector.
  10. At the sensor side, measure resistance between A/F sensor (Sensor 1) 4P connector terminals No. 3 and No. 4.
    Fig 2: Measuring Resistance Between A/F Sensor 4P Connector Terminals No. 3 And No. 4
    G05454502Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 2.0-2.6 Ω at room temperature? 

    YES  - Go to step  11.

    NO  - Go to step  32.

  11. At the sensor side, check for continuity between A/F sensor (Sensor 1) 4P connector terminals No. 2 and No. 3, and between terminals No. 2 and No. 4 individually.
    Fig 3: Checking Continuity Between A/F Sensor 4P Connector Terminals 2 And 3, And Between Terminals 2 And 4
    G05454503Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Go to step  32.

    NO  - Go to step  12.

  12. Jump the SCS line with the HDS.
  13. Disconnect ECM/PCM connector A (31P).
  14. Check for continuity between ECM/PCM connector terminal A10 and body ground.
    Fig 4: Checking Continuity Between ECM/PCM Connector Terminal A10 And Body Ground
    G05454504Courtesy 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  33.

    NO  - Go to step  15.

  15. Connect A/F sensor (Sensor 1) 4P connector terminal No. 4 to body ground with a jumper wire.
    Fig 5: Identifying A/F Sensor 4P Connector Terminal No. 4 To Body Ground With Jumper Wire
    G05454505Courtesy of AMERICAN HONDA MOTOR CO., INC.
  16. Check for continuity between ECM/PCM connector terminal A10 and body ground.
    Fig 6: Checking Continuity Between ECM/PCM Connector Terminal A10 And Body Ground
    G05454506Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Go to step  17.

    NO  - Repair open in the wire between the ECM/PCM (A10) and the A/F sensor (Sensor 1), then go to step  33.

  17. Connect A/F sensor (Sensor 1) 4P connector terminal No. 3 to body ground with a jumper wire.
    Fig 7: Identifying A/F Sensor 4P Connector Terminal No. 3 To Body Ground With Jumper Wire
    G05454507Courtesy of AMERICAN HONDA MOTOR CO., INC.
  18. Check for continuity between A/F sensor relay 4P connector terminal No. 2 and body ground.
    Fig 8: Checking Continuity Between A/F Sensor Relay 4P Connector Terminal No. 2 And Body Ground
    G05454508Courtesy 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, then go to step  33.

  19. Disconnect ECM/PCM connector E (31P).
  20. Check for continuity between ECM/PCM connector terminal E8 and A/F sensor relay 4P connector terminal No. 3.
    Fig 9: Checking Continuity Between ECM/PCM Connector Terminal E8 And A/F Sensor Relay 4P Connector Terminal No. 3
    G05454509Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Go to step  21.

    NO  -Repair open in the wire between the ECM/PCM (E8) and the A/F sensor relay, then go to step  33.

  21. Measure voltage between A/F sensor relay 4P connector terminal No. 1 and body ground.
    Fig 10: Measuring Voltage Between A/F Sensor Relay 4P Connector Terminal No. 1 And Body Ground
    G05454510Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES  - Go to step  22.

    NO  - Repair open in the wire between the A/F sensor relay and the No. 23 LAF (10 A) fuse or the No. 9 SMALL LIGHT (30 A) fuse, then go to step  33.

  22. Turn the ignition switch ON (II).
  23. Measure voltage between A/F sensor relay 4P connector terminal No. 4 and body ground.
    Fig 11: Measuring Voltage Between A/F Sensor Relay 4P Connector Terminal No. 4 And Body Ground
    G05454511Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES  - Go to step  39.

    NO  - Repair open in the wire between the A/F sensor relay and the No. 31 LAF (7.5 A) fuse, then go to step  33.

  24. Remove the A/F sensor relay (A).
    Fig 12: Identifying A/F Sensor Relay
    G05454512Courtesy of AMERICAN HONDA MOTOR CO., INC.
  25. Disconnect the A/F sensor (Sensor 1) 4P connector.
  26. Disconnect the EVAP canister vent shut valve 2P connector.
  27. Check for continuity between A/F senor (Sensor 1) 4P connector terminal No. 3 and body ground.
    Fig 13: Checking Continuity Between A/F Senor 4P Connector Terminal No. 3 And Body Ground
    G05454513Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Repair short in the wire between the A/F sensor (Sensor 1), the A/F sensor relay, and the EVAP canister vent shut valve. Also replace the No. 23 LAF (10 A) fuse, then go to step  33.

    NO  - Go to step  28.

  28. Disconnect the 14P connector from the under-dash fuse/relay box.
  29. Check for continuity between A/F sensor relay 4P connector terminal No. 1 and body ground.
    Fig 14: Checking Continuity Between A/F Sensor Relay 4P Connector Terminal No. 1 And Body Ground
    G05454514Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Repair short in the wire between the A/F sensor relay and the under-dash fuse/relay box. Also replace the No. 23 LAF (10 A) fuse, then go to step  33.

    NO  - Go to step  30.

  30. Remove the No. 31 LAF (7.5 A) fuse from under-dash fuse/relay box.
  31. Check for continuity between A/F sensor relay 4P connector terminal No. 4 and body ground.
    Fig 15: Checking Continuity Between A/F Sensor Relay 4P Connector Terminal No. 4 And Body Ground
    G05454515Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  - Repair short in the wire between the A/F sensor relay and the under-dash fuse/relay box. Also replace the No. 31 LAF (7.5 A) fuse, then go to step  33.

    NO  - Replace the dashboard wire harness, then go to step  33.

  32. Replace the A/F sensor (Sensor 1) (see A/F SENSOR REPLACEMENT ).
  33. Reconnect all connectors.
  34. Turn the ignition switch ON (II).
  35. Reset the ECM/PCM with the HDS.
  36. Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN PROCEDURE ).
  37. 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, and the ECM/PCM, then go to step  1.

    NO  - Go to step  38.

  38. 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 37, 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, and the ECM/PCM, then go to step  1. If the screen indicates NOT COMPLETED, go to step  36.

  39. Turn the ignition switch OFF.
  40. Reconnect all connectors.
  41. Update the ECM/PCM if it does not have the latest software (see UPDATING THE ECM/PCM ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ).
  42. Start the engine.
  43. 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, 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  42. If the ECM/PCM was substituted, go to step  1.

    NO  - Go to step  43.

  44. 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 43, 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, 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  40. If the ECM/PCM was substituted, go to step  1. If the screen indicates NOT COMPLETED, let the engine idle until a result comes on.

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