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 through the IGN SW fuse. The indicator is normally on unless the EBCM switches the indicator off, by energizing the ABS indicator lamp relay. The EBCM tests the ABS indicator lamp circuit with a 2 second bulb check, when the ignition is turned to RUN or the vehicle is started, the EBCM turns the indicator off. If the EBCM senses that a fault has occurred, it will set a DTC and light the ABS indicator lamp by de-energizing the ABS indicator lamp relay. In the backup mode, the ABS indicator lamp relay circuit will ensure that the ABS indicator lamp is illuminated, if the 24-way EBCM connector is disconnected or poorly seated, or if the EBCM has failed during normal operation. If either of these fault conditions occur, the ABS indicator lamp relay will de-energize, which connects a ground path to the ABS indicator lamp circuit through terminals C1 and C2 of the ABS indicator lamp relay. This system ensures that the ABS indicator lamp will always be turned on if the following conditions exist:
| • | Open or high resistance in CKT 867 |
| • | The EBCM is faulty |
Diagnostic Aids
If the ABS indicator lamp is off always with no DTCs set (never turns on at bulb check, with the vehicle started or with the ignition switch in the RUN position), an open or high resistance in the lamp circuit is present between the instrument panel and the EBCM. Also check for an open instrument panel fuse or an open bulb.
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 manually (with fused jumper) turns on the ABS indicator lamp by bypassing the ABS indicator relay.
-
This step checks for a short to ground in CKT 1899.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
Does the ABS indicator lamp turn on? | -- | |||
Jumper terminal C4 of the relay center harness connector to ground. Does the ABS indicator lamp turn on? | -- | |||
4 | Using a J 39200 , measure the resistance between the relay center harness connector terminal C3 and ground. Is the resistance measurement within the specified range? | 0-2 ohms | ||
Using a J 39200 , measure the resistance between the relay center harness connector terminal C2 and ground. Is the resistance measurement equal to the specified value? | OL | |||
6 |
Is the ABS indicator lamp off constantly? | -- | Go to Diagnostic Aids | |
7 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- |
8 | Inspect for an open ABS indicator lamp. Is the ABS indicator lamp open? | -- | ||
9 | Repair the open or the high resistance in CKT 867. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
10 | Replace the ABS indicator lamp. Refer to Instrument Cluster Bulb Replacement in Lighting Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
11 | Repair the open or the high resistance in CKT 150. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
12 | Repair the short to ground in CKT 1899. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
13 | Replace the ABS indicator relay. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
