DTC Troubleshooting: C0023-12
DTC C0023-12: Brake Diag Circuit ON Failure
NOTE: Before you troubleshoot, review the general troubleshooting information.

DTC Description
DTC
C0023-12 Brake Diag Circuit ON Failure
  

1.
Problem verification:

Problem verification
?1.
Turn the vehicle to the ON mode.

?2.
Clear the DTC with the HDS.


?3.
Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

?4.
Wait for 1 second or more without pressing the brake pedal.

?5.
Check for DTCs with the HDS.
DTC Description
DTC
C0023-12 Brake Diag Circuit ON Failure
  

Is DTC C0023-12 indicated?

     
YES
     
     
     
The failure is duplicated. Go to step 2.
     
NO
     
     
     
Intermittent failure, the system is OK at this time. Refer to intermittent failures troubleshooting.?
2.
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
     
     
     
Replace the brake light relay.?
     
NO
     
     
     
Go to step 3.
3.
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 4.
     
NO
     
     
     
Go to step 5.
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. Check for loose terminals and poor connections in the VSA modulator-control unit 38P 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.?
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 more than 1 minute.


?3.
Disconnect the following connectors.
PCM connector A (51P)
Brake pedal position switch 4P connector

?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 (female terminals) No. 1:
 
PCM connector A (51P) No. 37


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:

PCM check
?1.
Substitute a known-good PCM.

?2.
Reconnect the following connectors.
PCM connector A (51P)
Brake pedal position switch 4P connector

?3.
Clear the DTC with the HDS.


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

?5.
Wait for 1 second or more without pressing the brake pedal.

?6.
Check for DTCs with the HDS.
DTC Description
DTC
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 38P 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