Circuit Description
The amber ABS indicator lamp operates in two modes; normal and backup. In the normal mode, ignition voltage is supplied to the ABS indicator lamp bulb through the IGN SW fuse. Once the ignition is turned on or the vehicle is started the EBCM energizes the ABS indicator lamp relay (normally closed) and ground path for the light through the relay is opened. The EBCM also illuminates the ABS indicator lamp for a 2 second bulb check by suppling ground through connector C2, terminal 1, If the EBCM senses a failure and a DTC is set, it will illuminate the lamp in this manner. In the backup mode, the ABS telltale relay circuit will ensure that the ABS indicator lamp is illuminated if the 24-way connector is disconnected or poorly seated, or if certain EBCM internal failures during normal operation. If either of these conditions occur, the ABS indicator lamp relay closes, which creates an alternate ground path to the ABS indicator lamp circuit through terminal B8 and terminal A7 of the EBCM. This system ensures that the ABS indicator lamp will always be turned on if the following conditions exist:
Conditions for Setting the DTC
| • | High voltage is present on the ABS indicator lamp control circuit when low voltage is expected (lamp is turned on). |
| • | Anything that keeps the ABS indicator lamp circuit high when the lamp is expected to be on. |
Action Taken When the DTC Sets
The ABS is not disabled.
Conditions for Clearing the DTC
| • | Repair the conditions responsible for setting the DTC. |
| • | Use the Scan Tool Clear DTCs function |
Diagnostic Aids
DTC C0286 typically sets because of a shorted ABS indicator lamp. Yet DTC C0286 can also set because of a short to voltage in the wiring between the ABS indicator lamp and the EBCM.
Test Description
The numbers below refer to the steps in the diagnostic table:
-
This step checks for normal operation of the ABS indicator lamp.
-
This step turns off the ABS indicator lamp with a J 36169-A .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | |
| -- | Go to Step 5 | Go to Step 3 | |
Does the ABS indicator lamp turn off? | -- | Go to Step 5 | Go to Step 4 | |
4 |
Is the voltage equal to or greater than the specified value? | 10 V | Go to Step 7 | Go to Step 8 |
5 |
Does DTC C0286 set as a current DTC? | -- | Go to Step 6 | Go to Diagnostic Aids |
6 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement Is repair complete? | -- | -- | |
7 | Repair a short to voltage in CKT 1899. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
8 | Replace the ABS indicator relay. Is the repair complete? | -- | -- |
