Circuit Description
The electronic brake control module (EBCM) controls the operation of the amber ABS warning lamp by means of a lamp driver module contained within the cluster.
Battery voltage is supplied to the instrument panel (I/P) cluster terminal B14, and the electronic brake control module terminal 4 when the ignition switch is turned ON. EBCM terminals 9 and 25 are hot at all times.
The default state is for the lamp driver module to turn ON the amber ABS warning lamp, by supplying a ground path through the lamp driver module.
When the EBCM commands the ABS lamp OFF, the EBCM will ground the ABS warning lamp control circuit. This causes the lamp driver module to open the path to ground for the bulb.
When the ignition switch is turned to the ON position, the EBCM turns ON the ABS warning lamp for 3 seconds for a bulb check.
Whenever a malfunction is detected within the ABS system, the EBCM turn ON the ABS warning lamp, notifying the driver that the ABS needs to be serviced.
Diagnostic Aids
Typical causes of the ABS warning lamp inoperative with no DTCs set.
| • | Faulty ABS bulb/loose socket |
| • | I/P fuse open |
| • | Faulty cluster/lamp driver module |
| • | Faulty EBCM |
| • | Grounded circuit between the EBCM and the cluster |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Component Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Did the amber ABS lamp turn ON? | B+ | Go to Step 3 | Go to Step 4 |
3 | Replace the EBCM. Refer to Brake Pressure Modulator Valve Assembly Replacement . Did you completer the replacement? | -- | System OK | -- |
4 | Check the cluster fuse. Is the fuse and terminal contact OK? | -- | Go to Step 6 | Go to Step 5 |
5 |
Did you find and correct the condition? | -- | System OK | -- |
6 |
Was the socket and the bulb OK? | -- | Go to Step 8 | Go to Step 7 |
7 | Replace the bulb/socket as needed. Did you complete the replacement? | -- | System OK | -- |
8 |
Was the voltage within the specified value? | B+ | Go to Step 10 | Go to Step 9 |
9 | Find and repair the source of low voltage on the cluster voltage supply terminal. Did you find and correct the condition? | -- | System OK | -- |
10 |
Was the resistance measured less than the specified value? | 2 Ω | Go to Step 12 | Go to Step 11 |
11 | Repair the open or high resistance between the cluster and the LDM. Did you find and correct the condition? | -- | System OK | -- |
12 |
Was the resistance within the specified value? | OL (open circuit) | Go to Step 14 | Go to Step 13 |
13 | Find the repair to the short to ground between the cluster harness and the EBCM harness. Did you find and correct the condition? | -- | System OK | -- |
14 | Replace the LDM. Did you complete the replacement? | -- | System OK | Go to Step 15 |
15 | Replace the cluster assembly. Refer to Instrument Cluster Replacement . Did you complete the replacement? | -- | System OK | -- |
