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

NOTE:  Before you troubleshoot, review the general troubleshooting information - Refer to: How to Troubleshoot the Fuel and Emissions SystemsHow to Troubleshoot the CVT System(CVT System) .

DTC (PGM-FI)

• 1. Problem verification:

  - 1. Turn the vehicle to the ON mode.

  - 2. Clear the DTC with the HDS.

  - 3. Start the engine.

  - 4. Check for Pending or Confirmed DTCs with the HDS.

  DTC Description	Confirmed DTC	Pending DTC	Freeze Frame
  P0135 A/F Sensor (Sensor 1) Heater Circuit Malfunction

  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 PCM. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot.

• 2. Fuse check:

  - 1. Turn the vehicle to the OFF (LOCK) mode.

  - 2. Check the following fuse.

  Fuse	No. A18 (15 A)
  Location	Under-hood fuse/relay box

  Is the fuse OK?

  YES 

  Go to step 3.

  NO 

  Go to step 10.

• 3. Relay check:

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

  Courtesy of HONDA, U.S.A., INC.

  - 2. Test the PGM-FI subrelay .

  Is the relay OK?

  YES 

  Go to step 4.

  NO 

  Replace the PGM-FI subrelay.

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

  - 1. Disconnect the following connector.

  A/F sensor (Sensor 1) 4P connector

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

  Test condition	Vehicle OFF (LOCK) mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  Test point 1	A/F sensor (Sensor 1) 4P connector No. 3 (A/F sensor (Sensor 1) side)
  Test point 2	A/F sensor (Sensor 1) 4P connector No. 4 (A/F sensor (Sensor 1) side)

  Courtesy of HONDA, U.S.A., INC.

  Is there 2.0-2.7 Ω at room temperature-

  YES 

  Go to step 5.

  NO 

  Replace the A/F sensor (Sensor 1) .

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

  - 1. At the sensor side, check for continuity between test points 1 and 2.

  Test condition	Vehicle OFF (LOCK) mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  Test point 1	A/F sensor (Sensor 1) 4P connector No. 1 (A/F sensor (Sensor 1) side)
  Test point 2	A/F sensor (Sensor 1) 4P connector No. 3 (A/F sensor (Sensor 1) side)

  Test point 1	A/F sensor (Sensor 1) 4P connector No. 1 (A/F sensor (Sensor 1) side)
  Test point 2	A/F sensor (Sensor 1) 4P connector No. 4 (A/F sensor (Sensor 1) side)

  Courtesy of HONDA, U.S.A., INC.

  Is there continuity?

  YES 

  Replace the A/F sensor (Sensor 1) .

  NO 

  Go to step 6.

• 6. Shorted wire check (AFHT line):

  - 1. Jump the SCS line with the HDS, and wait more than 1 minute.

  - 2. Disconnect the following connector.

  PCM connector C (51P)

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

  Test condition	Vehicle OFF (LOCK) mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  	PCM connector C (51P): disconnected
  Test point 1	PCM connector C (51P) No. 7
  Test point 2	Body ground

  Is there continuity?

  YES 

  Repair a short in the AFHT wire between the PCM (C7) and the A/F sensor (Sensor 1).

  NO 

  The AFHT wire is not shorted. Go to step 7.

• 7. Open wire check (AFHT line):

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

  Test condition	Vehicle OFF (LOCK) mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  	PCM connector C (51P): disconnected
  Test point 1	A/F sensor (Sensor 1) 4P connector No. 3

  Test point 2

  PCM connector C (51P) No. 7

  Courtesy of HONDA, U.S.A., INC.

  Is there continuity?

  YES 

  The AFHT wire is OK. Go to step 8.

  NO 

  Repair an open in the AFHT wire between the PCM (C7) and the A/F sensor (Sensor 1).

• 8. Open wire check (LAF+/FI SUB RLY OUT line):

  - 1. Turn the vehicle to the ON mode.

  - 2. Measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  	PCM connector C (51P): disconnected
  Test point 1	A/F sensor (Sensor 1) 4P connector No. 4
  Test point 2	Body ground

  Courtesy of HONDA, U.S.A., INC.

  Is there battery voltage?

  YES 

  The LAF+/FI SUB RLY OUT wire is OK. Go to step 9.

  NO 

  Repair an open in the LAF+/FI SUB RLY OUT wire between the A/F sensor (Sensor 1) and the PGM-FI subrelay.

• 9. Open wire check (FI SUB RLY CL- line):

  - 1. Turn the vehicle to the OFF (LOCK) mode.

  - 2. Jump the SCS line with the HDS, and wait more than 1 minute.

  - 3. Disconnect the following connector.

  PCM connector A (51P)

  - 4. Turn the vehicle to the ON mode.

  - 5. Measure the voltage between test points 1 and 2.

  Test condition	Vehicle ON mode
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  	PCM connector B (51P): disconnected
  	PCM connector A (51P): disconnected
  Test point 1	PCM connector A (51P) No. 16
  Test point 2	Body ground

  Is there battery voltage?

  YES 

  The FI SUB RLY CL- wire is OK. Update the PCM if it does not have the latest software, or substitute a known-good PCM , then recheck. If DTC P0135 goes away and the PCM was updated, troubleshooting is complete. If DTC P0135 goes away and the PCM was substituted, replace the original PCM .

  NO 

  Repair an open in the FI SUB RLY CL- wire between the PCM (A16) and the PGM-FI subrelay.

• 10. Shorted wire check (LAF+/FI SUB RLY OUT line):

  - 1. Remove the No. A8 (7.5 A) fuse and the No. A18 (15 A) fuse from the under-hood fuse/relay box.

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

  Courtesy of HONDA, U.S.A., INC.

  - 3. Disconnect the following connectors.

  A/F sensor (Sensor 1) 4P connector

  EVAP canister vent shut valve 2P connector (USA and Canada models)

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

  Test condition	Vehicle OFF (LOCK) mode
  	No. A8 (7.5 A) fuse: removed
  	No. A18 (15 A) fuse: removed
  	PGM-FI subrelay: disconnected
  	A/F sensor (Sensor 1) 4P connector: disconnected
  	EVAP canister vent shut valve 2P connector: disconnected
  Test point 1	A/F sensor (Sensor 1) 4P connector No. 4

  Test point 2

  Body ground

  Courtesy of HONDA, U.S.A., INC.

  Is there continuity?

  YES 

  Repair a short in the LAF+/FI SUB RLY OUT wire between the A/F sensor (Sensor 1), the PGM-FI subrelay, No. A8 (7.5 A) fuse, and the EVAP canister vent shut valve (USA and Canada models). Also replace the No. A18 (15 A) fuse.

  NO 

  The LAF+/FI SUB RLY OUT wire is OK. Replace the No. A18 (15 A) fuse, then recheck. If the fuse is blown again, replace the under-hood fuse/relay box .