DTC Troubleshooting: P0135 (K20C1) - Honda Civic FC/FK 2016-2021

1.

Problem verification:

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
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 relay circuit board (PGM-FI subrelay circuit), and the PCM. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot.?

2.

Fuse check:

Fuse check

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

?2.

Check the following fuse.

Fuse	No. A9 (15 A)
Location	Under-hood fuse/relay box

Is the fuse OK?


	YES

Go to step 3.


	NO

Repair a short in the +B DBW wire between the No. A9 (15 A) fuse and the relay circuit board or in the IGPS(LAF)/FI SUB RLY OUT wire between the A/F sensor (Sensor 1) and the relay circuit board. Also replace the No. A9 (15 A) fuse.?

3.

Relay circuit board check:

Relay circuit board check

?1.	Remove and test the relay circuit board.

Is the relay circuit board OK?


	YES

Go to step 4.


	NO

Replace the relay circuit board.?

4.

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

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

?1.

Disconnect the following connector.

A/F sensor (Sensor 1) 6P connector

?2.

At the A/F sensor (Sensor 1) side, measure the resistance between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected
Test point 1	A/F sensor (Sensor 1) 6P connector (male terminals) No. 2 (sensor side):
Test point 2	A/F sensor (Sensor 1) 6P connector (male terminals) No. 5 (sensor side):

Is there 2.4?4.0 ? 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 (short to ground):

A/F sensor (Sensor 1) internal circuit check (short to ground)

?1.

At the A/F sensor (Sensor 1) side, check for continuity between the following test points and body ground individually.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected

Connector	Terminal
A/F sensor (Sensor 1) 6P connector (male terminals) (sensor side):	No. 1
	No. 2
	No. 3
	No. 4
	No. 5
	No. 6

Is there continuity at any terminal?


	YES

Replace the A/F sensor (Sensor 1).?


	NO

Go to step 6.

6.

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

A/F sensor (Sensor 1) internal circuit check

?1.

At the A/F sensor (Sensor 1) side, check for continuity between the following test points and the A/F sensor (Sensor 1) 6P connector (male terminals) No. 2 individually.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected

Connector	Terminal
A/F sensor (Sensor 1) 6P connector (male terminals) (sensor side):	No. 1
	No. 3
	No. 4
	No. 6

Is there continuity at any terminal?


	YES

Replace the A/F sensor (Sensor 1).?


	NO

Go to step 7.

7.

Shorted wire check (AFHT line):

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 No. 1 (96P)

?3.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected
	PCM connector No. 1 (96P): disconnected
Test point 1	PCM connector No. 1 (96P) No. 16
Test point 2	Body ground

Is there continuity?


	YES

Repair a short in the AFHT wire between PCM connector No. 1 terminal No. 16 and the A/F sensor (Sensor 1).?


	NO

The AFHT wire is not shorted. Go to step 8.

8.

Open wire check (AFHT line):

Open wire check (AFHT line)

?1.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected
	PCM connector No. 1 (96P): disconnected
Test point 1	A/F sensor (Sensor 1) 6P connector (female terminals) No. 5:
Test point 2	PCM connector No. 1 (96P) No. 16

Is there continuity?


	YES

The AFHT wire is OK. Go to step 9.


	NO

Repair an open in the AFHT wire between PCM connector No. 1 terminal No. 16 and the A/F sensor (Sensor 1).?

9.

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

Open wire check (FI SUB RLY CL- line)

?1.

Disconnect the following connector.

PCM connector No. 2 (58P)

?2.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Relay circuit board: removed
	A/F sensor (Sensor 1) 6P connector: disconnected
	PCM connector No. 1 (96P): disconnected
	PCM connector No. 2 (58P): disconnected
Test point 1	Relay circuit board connector B (6P) (female terminals) No. 2:
Test point 2	PCM connector No. 2 (58P) No. 47

Is there continuity?


	YES

The FI SUB RLY CL- wire is OK. Go to step 10.


	NO

Repair an open in the FI SUB RLY CL- wire between PCM connector No. 2 terminal No. 47 and the relay circuit board.?

10.

Open wire check (IGPS(LAF)/FI SUB RLY OUT line):

Open wire check (IGPS(LAF)/FI SUB RLY OUT line)

?1.	Reconnect PCM connector No. 2 (58P).

?2.	Reinstall the relay circuit board.

?3.	Exit the SCS mode with the HDS.

?4.	Turn the vehicle to the ON mode.

?5.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode
	A/F sensor (Sensor 1) 6P connector: disconnected
	PCM connector No. 1 (96P): disconnected
Test point 1	A/F sensor (Sensor 1) 6P connector (female terminals) No. 2:
Test point 2	Body ground

Is there battery voltage?


	YES

The IGPS(LAF)/FI SUB RLY OUT wire is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM, then recheck. If DTC P0135 goes away and the PCM was substituted, replace the original PCM.?


	NO

Repair an open in the IGPS(LAF)/FI SUB RLY OUT wire between the A/F sensor (Sensor 1) and the relay circuit board.?