Circuit Description
This DTC is used to identify the conditions of the brake switch circuit. The electronic brake control module (EBCM) sends a low current 5-volt sense voltage on the brake switch input line to the rear brake light bulbs. If the rear brake light circuit is intact, this voltage will be pulled low, under 1 volt, to ground through the rear brake light bulbs. When the brake light switch is depressed, battery voltage will be supplied to the rear brake lights and to the EBCM, indicating the brake lights are ON.
Conditions for Setting the DTC
| • | Brake switch contacts open |
| • | Brake switch fuse open |
| • | Brake switch fuse power feed circuit open |
| • | Brake switch misadjusted |
| • | Internal EBCM fault |
Action Taken When the DTC Sets
The antilock brake system (ABS) remains functional.
Conditions for Clearing the DTC
| • | If the conditions that the DTC C0091 no longer presents, the DTC can be cleared by scan tool. |
| • | The DTC that has not occurred in 100 drive cycles will be cleared from the history data. |
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check-ABS? | Go to Step 2 | |
2 |
Did you find any other DTCs? | Go to Step 3 | |
3 | Apply the brake pedal. Is the rear brake lamp turned ON? | Go to Step 4 | Go to Step 5 |
4 | Refer to Conditions for Setting the DTC C0091. Did you find and correct the condition? | System OK | -- |
5 |
Does the brake switch indicate ON? | Go to Step 6 | Go to Step 7 |
6 |
Did you complete the replacement? | System OK | -- |
7 | Inspect any short or open from the brake switch wiring harness terminal 3 and 4. Did you find any faults for those terminals? | Go to Step 8 | -- |
8 |
Did you find any DTCs? | Go to Step 9 | |
9 | Inspect the EBCM connector. Did you find any fault from the EBCM connector? | Go to Step 8 | Go to Step 10 |
10 | Replace the EBCM. Did you complete the replacement? | Go to Step 1 | -- |
