For 1990-2009 cars

### Circuit Description

The electronic brake control module (EBCM) controls the operation of the red brake warning lamp by means of a lamp driver module (LDM) 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.

When the EBCM commands the brake warning lamp OFF, the EBCM will ground the brake warning lamp control circuit. This causes the LDM 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 general brake system or de-coupled dynamic rear proportioning (DDRP), the EBCM may turn ON the brake warning lamp, notifying the driver that either brake system or DDRP needs to be serviced.

### Diagnostic Aids

Typical causes of the ABS warning lamp inoperative with no DTCs set:

• | Faulty bulb/loose socket

• | I/P fuse open

• | Faulty cluster/LDM

• | Faulty EBCM

• | Grounded circuit between the EBCM and the cluster

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic Starting Point - Hydraulic Brakes? | -- | Go to Step 2 | Go to Diagnostic Starting Point - Hydraulic Brakes
2 |

1. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
2. Turn ON the ignition switch.

Did the brake warning lamp turn ON?

--

Go to Step 3

Go to Step 4

3 | Replace the EBCM. Did you complete 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 |

1. Replace the open fuse and/or repair the loose terminals.
2. Find the short, which caused the fuse to open, if applicable.

Did you find and correct the condition?

--

System OK

--

6 | Remove the brake warning lamp bulb from the cluster and inspect for an open bulb filament or poor socket contact? Was the socket and 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 |

1. Turn OFF the ignition switch.
2. Verify the EBCM harness is still disconnected.
3. Remove the cluster assembly from the instrument panel.
4. Disconnect the white cluster harness connector from the cluster assembly.
5. Turn ON the ignition, with the engine OFF.
6. Connect a voltmeter to terminal B14 of the cluster harness and then to body ground.

Does the voltage measure within the specified range?

11-14 V

Go to Step 10

Go to Step 9

9 | Find and repair the source of the low voltage on the cluster voltage supply terminal. Did you find and correct the condition? | -- | System OK | --
10 |

1. Turn OFF the ignition switch.
2. Disconnect the white cluster harness connector from the cluster assembly.
3. Connect an ohmmeter between the white cluster harness terminal C2 and the lamp driver module (LDM) harness terminal 3.

Does the resistance measure less than the specified value?

2 ohms

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 |

1. Turn OFF the ignition switch.
2. Verify the LDM harness and EBCM harness are still disconnected.
3. Connect an ohmmeter to the EBCM harness terminal B3 and then to body ground.

Does the resistance measure within the specified range?

OL (Open Circuit)

Go to Step 14

Go to Step 13

13 | Find and repair the short to ground between the LDM 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 | --