Circuit Description
The electronic brake control module (EBCM) controls the operation of the brake 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 11, and the electronic brake control module terminal 13 when the ignition switch is turned ON. EBCM terminals 1 and 2 are hot at all times.
The default state is for the lamp driver module to turn ON the brake warning lamp, by supplying a ground path through the lamp driver module.
When the EBCM commands the brake warning lamp OFF, the EBCM will ground the brake 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 antilock brake system (ABS) warning lamp for 3 seconds for a bulb check.
Whenever a malfunction is detected within the general brake system or DBC7 ABS system, the EBCM may turn ON the brake warning lamp, notifying the driver that either the brake system or brake modulator system needs to be serviced.
Diagnostic Aids
Typical causes of the brake warning lamp ON with no DTCs set:
| • | Faulty emergency brake switches |
| • | Low brakes fluid level or faulty brake fluid switch |
| • | DDPR is disabled due to the following fault conditions in DBC/7ABS system: |
| - | Two wheel speed sensors inoperative on same axle |
| - | Battery 2 motor input open or short to ground |
| - | Motor ground open or short to battery |
| - | ECU ground open or short to battery |
| - | Ignition open or short to ground |
| • | Grounded circuit between the cluster and the EBCM |
| • | Faulty cluster/lamp driver module |
| • | Faulty EBCM |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Observe antilock brake system (ABS) warning lamp. Is the ABS warning lamp ON also? | -- | Go to Step 4 | Go to Step 3 |
3 |
Did you find and correct the condition? | -- | System OK | -- |
4 | Connect the scan tool and retrieve DTCs. Does the scan tool display any DTCs? | -- | Go to Step 5 | |
5 |
Did the brake warning lamp turn OFF? | -- | Go to Step 6 | Go to Step 7 |
6 | Replace the EBCM. Did you complete the replacement? | -- | System OK | -- |
7 |
Was the resistance within the specified value? | OL (open circuit) | Go to Step 9 | Go to Step 8 |
8 | Find and repair the short to ground between the cluster harness and the LDM harness. Did you find and correct the condition? | -- | System OK | -- |
9 |
Was the resistance measured less than the specific value? | 2 ohms | Go to Step 11 | Go to Step 10 |
10 | Repair the open or high resistance between the LDM and the EBCM. Did you find and correct the condition? | -- | System OK | -- |
11 | Replace the LDM. Did you complete the replacement? | -- | System OK | Go to Step 12 |
12 | Replace the cluster assembly. Did you complete the replacement | -- | System OK | -- |
