Circuit Description
The electronic brake control module (EBCM) monitors brake pedal position through the stop lamp switch. The stop lamp switch is closed when the brake pedal is pressed and the stop lamp switch opens when the brake pedal is released. When the stop lamp switch is closed, the EBCM receives a voltage signal from the stop lamp switch. The stop lamp switch receives power from the STOP fuse.
Conditions for Running the DTC
DTC C1249 can be set anytime.
Conditions for Setting the DTC
The EBCM detects an open in the stop lamp switch circuit.
Action Taken When the DTC Sets
The EBCM turns ON the ABS indicator. If this DTC sets during an ABS event, the ABS will remain functional until the vehicle stops. Otherwise the ABS is disabled.
Conditions for Clearing the DTC
The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.
Diagnostic Aids
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.
The following are possible causes of the malfunction:
| • | An open STOP fuse, possible short to ground in its circuitry |
| • | Misadjusted stop lamp switch |
| • | Faulty stop lamp switch |
| • | Open or high resistance in the brake switch input circuit |
| • | Short to voltage in the brake switch input circuit |
| • | An internal EBCM malfunction |
If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
This step inspects the Stop Lamp Switch status with the switch OFF.
-
This step inspects the Stop Lamp Switch status with the switch applied.
-
This step ensures proper adjustment of the Stop Lamp Switch.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | |||
1 | Did you perform A Diagnostic System Check - ABS? | Go to Step 2 | |
Does the scan tool display Released? | Go to Step 3 | Go to Step 4 | |
Press the brake pedal while observing the Brake Switch parameter. Does the Brake Switch parameter change state? | Go to Diagnostic Aids | Go to Step 4 | |
Did you find and correct the condition? | Go to Step 11 | Go to Step 5 | |
5 |
Does the scan tool display Released? | Go to Step 8 | Go to Step 6 |
6 | Test the Brake Switch circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
7 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
9 | Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Assembly Replacement . Did you complete the replacement? | Go to Step 11 | -- |
10 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | Go to Step 11 | -- |
11 |
Does the DTC reset? | Go to Step 2 | System OK |
