DTC Troubleshooting: C0023-12

DTC C0023-12: Brake Diag Circuit ON Failure

NOTE: Before you troubleshoot, review the general troubleshooting information.

DTC Description	DTC	Freeze Frame
C0023-12 Brake Diag Circuit ON Failure

Brake light relay relay check:

Brake light relay check

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

?2.	Check the brake lights without pressing the brake pedal.

Are the brake lights on?


	YES

Replace the brake light relay.?


	NO

Go to step 2.

Shorted wire check (BRK LAMP line) 1:

Shorted wire check (BRK LAMP line) 1

?1.	Turn the vehicle to the ON mode.

?2.	Check the brake lights without pressing the brake pedal.

Are the brake lights on?


	YES

Go to step 3.


	NO

Go to step 4.

Shorted wire check (BRK LAMP line) 2:

Shorted wire check (BRK LAMP line) 2

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

?2.

Disconnect the following connector.

VSA modulator-control unit 38P connector

?3.	Turn the vehicle to the ON mode.

?4.	Check the brake lights without pressing the brake pedal.

Are the brake lights on?


	YES

Repair a short to body ground in the wire between the VSA modulator-control unit and the brake light relay.?


	NO

The BRK LAMP wire is OK. Go to step 7.

Problem verification:

Problem verification

?1.	Clear the DTC with the HDS.

?2.	Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

?3.	Press the brake pedal for 3 seconds or more.

?4.

Check for DTCs with the HDS.

DTC Description	DTC	Freeze Frame
C0023-12 Brake Diag Circuit ON Failure

Is DTC C0023-12 indicated?


	YES

The failure is duplicated. Go to step 5.


	NO

The failure is not duplicated. Go to step 7.

Open wire check (STOP SW line):

Open wire check (STOP SW 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 connectors.

Brake pedal position switch 4P connector

PCM connector A (51P)

?4.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Brake pedal position switch 4P connector: disconnected
	PCM connector A (51P): disconnected
Test point 1	Brake pedal position switch 4P connector No. 1
Test point 2	L4 engine: PCM connector A (51P) No.37
	V6 engine: PCM connector A (51P) No.25

Is there continuity?


	YES

The STOP SW wire is OK. Go to step 6.


	NO

Repair an open in the wire between the PCM and the brake pedal position switch.?

PCM check (update or substitution):

PCM check (update or substitution)

?1.

Reconnect the following connectors.

Brake pedal position switch 4P connector

PCM connector A (51P)

?2.	Update the PCM if it does not have the latest software, or substitute a known-good PCM.

?3.	Clear the DTC with the HDS.

?4.	Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

?5.	Press the brake pedal for 3 seconds or more.

?6.

Check for DTCs with the HDS.

DTC Description	DTC	Freeze Frame
C0023-12 Brake Diag Circuit ON Failure

Is DTC C0023-12 indicated?


	YES

Go to step 7.


	NO

If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM.?

VSA modulator-control unit check (update):

VSA modulator-control unit check (update)

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

?2.

Reconnect the following connector.

VSA modulator-control unit 38P connector (if disconnected)

?3.	Update the VSA modulator-control unit if it does not have the latest software.

?4.	Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

?5.	Press the brake pedal for 3 seconds or more.

?6.

Check for DTCs with the HDS.

DTC Description	DTC	Freeze Frame

Is DTC C0023-12 indicated?


	YES

Check for loose terminals in the VSA modulator-control unit 38P connector. If the VSA modulator-control unit was updated and the symptom/indication is still present, replace the VSA modulator-control unit.?


	NO

Troubleshooting is complete. If any other DTCs are indicated, go to the indicated DTCs troubleshooting.?