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 contained within the cluster.

Battery voltage is supplied to the 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.

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 turn ON the ABS warning lamp for 3 seconds for a bulb check.

Whenever a malfunction is detected within the general brake system or DDRP, the EBCM may turns 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/lamp driver module

• | Faulty EBCM

• | Grounded circuit between the EBCM and the cluster

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you review the brake warning system circuit description and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms - Hydraulic Brakes
2 |

1. Disconnect the 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. Is the fuse and the terminal contact OK? | -- | System OK | --
4 | Check the cluster fuse. Did you complete the replacement? | -- | 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. 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 the ignition switch ON.
6. Connect a voltmeter to terminal 11 of the white cluster harness and then to body ground.

Was the voltage within the specified value?

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 6 and the lamp driver module (LDM) harness terminal A.

Was the resistance measured 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. The LDM harness and EBCM harness still are disconnected.
3. Connect an ohmmeter to the EBCM harness terminal 18 and then to body ground.

Was the resistance within the specified value?

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. Did you complete the replacement? | -- | System OK | --