Circuit Description
This circuit detects an open stoplamp/BTSI switch in the non-ABS mode. The EBCM/EBTCM looks for a deceleration rate that indicates braking action and requires several repeats of this detection method in order to verify this assumption. In each case, the TCS will not be available since the EBCM/EBTCM detects no stoplamp/BTSI switch voltage.
Conditions for Setting the DTC
The stoplamp switch remains open for 3 deceleration cycles.
Action Taken When the DTC Sets
| • | A DTC C1291 is stored |
| • | The TCS is disabled |
| • | The TRACTION OFF indicator turns on |
| • | The ABS remains functional |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and you used the scan tool Clear DTC function. |
| • | The EBCM/EBTCM does not detect the DTC in 50 drive cycles. |
Diagnostic Aids
| • | Thoroughly inspect the wiring and the connectors. Failure to carefully and fully inspect the wiring and the connectors can result in misdiagnosis. Misdiagnosis may cause replacement of parts without repairing the malfunction. |
| • | If any WSS DTCs are present, diagnose the WSS DTCs first. |
| • | The following conditions may cause most intermittent malfunctions: |
| - | Poor connections |
| - | Rubbed through wire insulation |
| - | A broken wire inside the insulation |
| • | The following conditions are other possible causes for this malfunction: |
| - | An open stoplamp/BTSI switch |
| - | An open brake fuse |
| - | A misadjusted stoplamp/BTSI switch |
| - | Erratic wheel speeds |
| - | A wiring problem, terminal corrosion, or a poor connection in the circuit |
| • | If an intermittent malfunction exists, refer to Testing for Electrical Intermittents in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks if the Stoplamp Switch and Power Distribution are OK.
-
This step checks for voltage at the EBTCM.
-
This step checks the Stoplamp Switch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 | Are any wheel speed sensor DTCs present? | -- | ||
Press the brake pedal. Do the brake lights come on? | -- | |||
Is the voltage within the specified range? | Battery Voltage | |||
5 | Replace the EBTCM. Refer to Electronic Brake Control Module Replacement . Is the replacement complete? | -- | Go to Diagnostic System Check | -- |
6 | Repair the open or high resistance in CKT 20. Refer to Wiring Repairs . Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
7 | Inspect the STOP fuse in the underhood fuse block. Is the BRAKE fuse OK? | -- | ||
8 |
Is the voltage within the specified range? | Battery Voltage | ||
9 | Repair the open in CKT 640. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
Connect a fused jumper wire between the stoplamp/BTSI switch harness connector terminals A and B. Do the brake lamps come on? | -- | |||
11 | Adjust or repair the stoplamp/BTSI switch as necessary. Refer to Stop Lamp Switch Adjustment or Stop Lamp Switch Replacement in Hydraulic Brakes. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
12 |
Is the fuse OK? | -- | ||
13 | Repair the short to ground in CKT 640. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
14 |
Is the fuse OK? | -- | Go to Diagnostic System Check | |
15 |
Is the fuse OK? | -- | ||
16 | Repair the short to ground in CKT 20. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
