Circuit Description
When the brake pedal is depressed, the contacts on the brake light switch close to illuminate the brake lights. Battery voltage is also applied to terminal 14 of the electronic brake control module (EBCM), which signals the antilock brake system (ABS) controller that the brakes are applied and ABS may be needed. Without this, signals from a wheel speed sensor that may indicate a need for ABS intervention are questionable. When the brake pedal is not depressed, the EBCM terminal 14 is grounded through the brake lights.
This procedure will check whether there is no output or constant output from the brake light switch and will determine the cause as a faulty switch or a problem in the circuitry.
Conditions for Setting the DTC
| • | The ground connection or the positive connection at the EBCM has failed. |
| • | There is an open, short to ground, or short to positive in the vehicle wiring. |
| • | The brake light switch has failed. |
Action Taken When the DTC Sets
The system records a DTC C0161. The ABS and EBD operation is enabled and the ABS/EBD warning lamp doesn't turn ON.
Diagnostic Aids
Inspect wiring and connectors carefully and thoroughly. Failure to do so could result in misdiagnosis, causing part replacement with reappearance of the malfunction.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This simple test will isolate the problem to the fuse-brake light switch-splice 301 area or the splice 301-EBCM area.
-
This is the 1st step in identifying an open, a short to ground, a short to voltage, or a faulty brake light switch.
-
This step begins the process of finding an open, a defective connector, or a faulty EBCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Step on the brake pedal. Do the brake lights come on at all? | -- | Go to Step 3 | Go to Step 2 | |
2 | Remove your foot from the brake pedal. Do the lights stay on continuously? | -- | Go to Step 8 | Go to Step 11 |
Inspect fuse EF13 in the engine compartment fuse block. Is fuse EF13 open? | -- | Go to Step 4 | Go to Step 6 | |
4 |
Is the new fuse open? | -- | Go to Step 5 | Go to Step 7 |
5 |
Did you complete the action? | -- | System OK | -- |
6 | Repair the open in the brake light switch circuit OG/BK from terminal 6 of connector C102 at the engine fuse block to the brake light switch and circuit L-BU from terminal 11 of splice S301. Did you complete the repair? | -- | System OK | -- |
7 | Inspect for functioning of the brake lights and the antilock brake system (ABS) system. Did you complete the action? | -- | System OK | -- |
8 | Inspect the brake lamp switch adjustment. Refer to Stop Lamp Switch Adjustment in Lighting Systems. Did the switch adjustment correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 | Replace the brake lamp switch. Did you complete the repair? | -- | System OK | -- |
10 | Repair the short to positive in the circuit YE between the brake light switch, splice S301, the brake lights, the center high-mounted stop lamp, and the ABS wiring harness connector at the electronic brake control module (EBCM) terminal 14. Did you complete the repair? | -- | System OK | -- |
Does the voltage measure within the specified range? | 11-14 V | Go to Step 13 | Go to Step 12 | |
12 |
Did you complete the repair? | -- | System OK | -- |
13 | Inspect the interface between the ABS EBCM connector and the EBCM. Is there damage at the interface? | -- | Go to Step 14 | Go to Step 15 |
14 | Repair the connector or replace the wiring harness or the ABS unit as required. Did you complete the repair? | -- | System OK | -- |
15 | Replace the ABS unit. Did you complete the replacement? | -- | System OK | -- |
