DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P0135

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 How To Troubleshoot The Fuel And Emissions Systems.

1. Problem verification:

Problem verification
-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 Pending or Confirmed DTCs with the HDS.

Is DTC P0135 indicated?
-YES- The failure is duplicated. Go to step 2.
-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 PGM-FI subrelay, and the ECM/PCM.

2. Fuse check:

Fuse check
-1. Turn the ignition switch to LOCK (0).

-2. Check the following fuse.





Is the fuse OK?
-YES- Go to step 3.
-NO- Go to step 9.

3. Relay check:

Relay check
-1. Remove the PGM-FI subrelay (A) from the under-hood fuse/relay box.





-2. Test the PGM-FI subrelay. Testing and Inspection

Is the PGM-FI subrelay OK?
-YES- Go to step 4.
-NO- Replace the PGM-FI subrelay, then do the repair verification.

4. A/F sensor (Sensor 1) internal heater resistance check:

A/F sensor (Sensor 1) internal heater resistance check
-1. Disconnect the following connector.





-2. At the sensor side, measure the resistance between test points 1 and 2.









Is there 2.2-2.7 Ohms at room temperature?
-YES- Go to step 5.
-NO- Replace the A/F sensor (Sensor 1) A/F Sensor Removal and Installation, then do the repair verification.

5. A/F sensor (Sensor 1) internal circuit check:

A/F sensor (Sensor 1) internal circuit check
-1. At the sensor side, check for continuity between test points 1 and 2.














Is there continuity?
-YES- Replace the A/F sensor (Sensor 1) A/F Sensor Removal and Installation, then do the repair verification.
-NO- Go to step 6.

6. Open wire check (AFHT line):

Open wire check (AFHT line)
-1. Jump the SCS line with the HDS.

-2. Disconnect the following connector.





-3. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- The AFHT wire is OK. Go to step 7.
-NO- Repair an open in the AFHT wire between the ECM/PCM (C9) and the A/F sensor (Sensor 1), then do the repair verification.

7. Open wire check (IGPS(LAF+), FI_SUB_RLY_OUT lines):

Open wire check (IGPS(LAF+), FI_SUB_RLY_OUT lines)
-1. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- The IGPS(LAF+)/FI_SUB_RLY_OUT wires are OK. Go to step 8.
-NO- Repair an open in the IGPS(LAF+)/FI_SUB_RLY_OUT wire between the A/F sensor (Sensor 1) and the PGM-FI subrelay, then do the repair verification.

8. Open wire check (FI_SUB_RLY_CL-T line):

Open wire check (FI_SUB_RLY_CL- line)
-1. Disconnect the following connector.





-2. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- The FI_SUB_RLY_CL- wire is OK. Update the ECM/PCM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM/PCM Service and Repair, then do the repair verification.
-NO- Repair an open in the FI_SUB_RLY_CL- wire between the ECM/PCM (A20) and the PGM-FI subrelay, then do the repair verification.

9. Shorted wire check (IGPS(LAF+), FI_SUB_RLY_OUT lines):

Shorted wire check (IGPS(LAF+), FI_SUB_RLY_OUT lines)
-1. Remove the PGM-FI subrelay (A) and the A/C condenser fan relay (B) from the under-hood fuse/relay box.





-2. Jump the SCS line with the HDS.

-3. Disconnect the following connectors.





-4. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- Repair a short in the IGPS(LAF+)/FI_SUB_RLY_OUT wire between the PGM-FI subrelay and the A/F sensor (Sensor 1), the A/C condenser fan relay, and the EVAP canister vent shut valve. Also replace the No. A15 (15 A) fuse, then do the repair verification.
-NO- The IGPS(LAF+)/FI_SUB_RLY_OUT wires are OK. Replace the under-hood fuse/relay box, then do the repair verification.

Repair verification (OBD STATUS check):

-1. Turn the ignition switch to LOCK (0).

-2. Reconnect all connectors.

-3. Turn the ignition switch to ON (II).

-4. Reset the ECM/PCM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-5. Do the ECM/PCM idle learn procedure. ECM/PCM Idle Learn Procedure

-6. Monitor the OBD STATUS for DTC P0135 in the DTCs MENU with the HDS.

Does the HDS indicate PASSED, FAILED, or NOT COMPLETED?
-PASSED- Troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM Service and Repair. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.
-FAILED- Go to step 1 and recheck. If the ECM/PCM was updated, substitute a known-good ECM/PCM Service and Repair, then check the OBD STATUS again.
-NOT COMPLETED - Keep the test condition until a result comes on.