For 1990-2009 cars

### Circuit Description

Serial data is transmitted/received by the electronic brake control module (EBCM) through terminal 7. The EBCM is supplied with constant battery feed voltage through terminals 9 and 25, and switched ignition voltage through terminal 4. The EBCM ground is provided through terminal 8 and 24.

### Diagnostic Aids

Typical causes of no communication with the EBCM:

• | Poor terminal contact at the EBCM

• | Loss of EBCM ground to terminal 8 and 24

• | Loss of battery voltage at EBCM terminals 9 and/or 25

• | Loss of ignition voltage at EBCM 4

• | Open/grounded data line

• | Data line with high resistance

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 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn the ignition switch OFF.
2. Disconnect the electronic brake control module (EBCM) harness.
3. Connect a voltmeter to the EBCM harness terminal 9 and then to body ground.

Does the voltage measure within the specified range?

B+

Go to Step 4

Go to Step 3

3 |

1. Repair the source of the low voltage to terminal 9.
2. Inspect for an open fuse, poor terminal contact, or a grounded wire.

Did you find and correct the condition?

--

System OK

--

4 | Connect a voltmeter to the EBCM harness terminal 25 and then to the body ground. Does the voltage measure within the specified range? | B+ | Go to Step 6 | Go to Step 5
5 |

1. Repair the source of the low voltage to terminal 25.
2. Inspect for an open fuse, poor terminal contact, or a grounded wire.

Did you find and correct the condition?

--

System OK

--

6 |

1. Turn ON the ignition switch.
2. Connect a voltmeter to the EBCM harness terminal 4 and then to body ground.

Does the voltage measure within the specified range?

B+

Go to Step 8

Go to Step 7

7 |

1. Repair the source of the low voltage to terminal 4.
2. Inspect for an open fuse, poor terminal contact, or a grounded wire.

Did you find and correct the condition?

--

System OK

--

8 |

1. Turn the ignition switch OFF.
2. Connect an ohmmeter to the EBCM harness terminal 8 and 24 and then to body ground.

Does the resistance measure less than the specified value?

2 Ω

Go to Step 10

Go to Step 9

9 |

1. Repair the source of the high resistance between terminal 8 and 24.
2. Find and inspect the ground location where the circuit is secured to body ground.

Did you find and correct the condition?

--

System OK

--

10 |

1. Turn OFF the ignition switch.
2. Verify the EBCM harness is still disconnected from the EBCM.
3. Connect an ohmmeter to the EBCM harness terminal 7 and the data link connector (DLC) terminal 7.

Does the resistance measure less than the specified value?

2 Ω

Go to Step 12

Go to Step 11

11 | Repair the source the high resistance between terminal 7 and DLC terminal 7. Did you complete the repair? | -- | System OK | --
12 |

1. Turn the ignition switch OFF.
2. Verify the EBCM harness is still disconnected.
3. Connect an ohmmeter to the EBCM harness terminal 7 and then to body ground.

Does the resistance measure OL, open circuit?

--

Go to Step 14

Go to Step 13

13 | Find and repair the short to ground on the data line. Did you find and correct the condition? | -- | System OK | --
14 | Replace the EBCM. Did you complete the replacement? | -- | System OK | --