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
    

1.
Brake light 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
     
     
     
     
NO
     
     
     
Go to step 2.
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.
3.
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 46P 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 relay circuit board (built-in brake light relay).?
     
NO
     
     
     
Check for loose terminals and poor connections in the VSA modulator-control unit 46P connector terminal No. 34. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting. If they are OK, replace the VSA modulator-control unit.?
4.
Problem verification:

Problem verification
?1.
Clear the DTC with the HDS.


?2.
Turn the vehicle to the OFF (LOCK) mode, then to 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
     
     
     
Intermittent failure, the system is OK at this time. Refer to intermittent failures troubleshooting. 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.?
5.
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 for more than 1 minute.


?3.
Disconnect the following connectors.
Brake pedal position switch 4P connector
PCM connector A (50P)

?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 (50P): disconnected
Test point 1
Brake pedal position switch 4P connector No. 1
Test point 2
PCM connector A (50P) No. 26


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.?
6.
PCM check (substitution):

PCM check (substitution)
?1.
Reconnect the following connectors.
Brake pedal position switch 4P connector
PCM connector A (50P)

?2.
Substitute a known-good PCM.

?3.
Clear the DTC with the HDS.


?4.
Turn the vehicle to the OFF (LOCK) mode, then to 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
     
     
     
Check for loose terminals and poor connections in the VSA modulator-control unit 46P connector. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting. If they are OK, replace the VSA modulator-control unit.?
     
NO