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 ).

Turn the ignition switch ON (II).
Clear the DTC with the HDS.
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.
Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0135 indicated?
1. YES- Go to step 5.
2. NO- Intermittent failure, 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.
Turn the ignition switch OFF.
Check these fuses:
- No. 14 OP1 (40 A) fuse in the under-hood fuse/relay box.
- No. 4 ACG (10 A) fuse in the under-dash fuse/relay box.
- No. 15 LAF (A/F) HEATER (20 A) fuse in the under-dash fuse/relay box.
Are any of the fuses blown?
1. YES- Repair short in the wire between the A/F sensor relay and the fuses. Also replace the blown fuses, then go to step 24.
2. NO- Go to step 7.
Disconnect the A/F sensor (Sensor 1) 4P connector.
At the sensor side, measure 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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there 2.1-2.9 Ω at room temperature?
1. YES- Go to step 9.
2. NO- Go to step 23.
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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Go to step 23.
2. NO- Go to step 10.
Jump the SCS line with the HDS.
Disconnect ECM/PCM connector A (31P).
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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Repair short in the wire between the ECM/PCM (A10) and the A/F sensor (Sensor 1), then go to step 24.
2. NO- Go to step 13.
Connect A/F sensor (Sensor 1) 4P connector terminal No. 3 to body ground with a jumper wire.

Fig 4: Connecting A/F Sensor (Sensor 1) 4P Connector Terminal No. 3 To Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Go to step 15.
2. NO- Repair open in the wire between the ECM/PCM (A10) and the A/F sensor (Sensor 1), then go to step 24.
Remove the glove box (see GLOVE BOX REMOVAL/INSTALLATION ).
Remove the A/F sensor relay (A).

Fig 6: Removing A/F Sensor Relay
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Connect A/F sensor (Sensor 1) 4P connector terminal No. 4 to body ground with a jumper wire.

Fig 7: Connecting A/F Sensor (Sensor 1) 4P Connector Terminal To Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check for continuity between A/F sensor relay 4P connector terminal No. 1 and body ground.

Fig 8: Checking Continuity Between A/F Sensor Relay 4P Connector Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Go to step 19.
2. NO- Repair open in the wire between the A/F sensor (Sensor 1) and the A/F sensor relay, then go to step 24.
Disconnect ECM/PCM connector E (31P).
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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Repair short in the wire between the ECM/PCM (E8) and the A/F sensor relay, then go to step 24.
2. NO- Go to step 21.
Check for continuity between ECM/PCM connector terminal E8 and A/F sensor relay 4P connector terminal No. 3.

Fig 10: Checking Continuity Between ECM/PCM Connector Terminal E8
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES- Go to step 22.
2. NO- Repair open in the wire between the ECM/PCM (E8) and the A/F sensor relay, then go to step 24.
Check the A/F sensor relay (see POWER RELAY TEST ).
Is the A/F sensor relay OK?
1. YES- Go to step 30.
2. NO- Replace the A/F sensor relay, then go to step 24.
Replace the A/F sensor (Sensor 1) (see A/F SENSOR REPLACEMENT ).
Reconnect all connectors.
Turn the ignition switch ON (II).
Reset the ECM/PCM with the HDS.
Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN PROCEDURE ).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES- If DTC P0135 is indicated, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO- Go to step 29.
Monitor the OBD STATUS for DTC P0135 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
1. YES- Troubleshooting is complete.
2. 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, go to step 26 and recheck.
Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM (see ECM/PCM UPDATING AND SUBSTITUTION FOR TESTING ).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES- If DTC P0135 is indicated, 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 any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO- If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see MAP SENSOR REPLACEMENT ).