For 1990-2009 cars

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.

1. A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.

1. The EBCM which was not communicating may have detected a short to voltage on one or both of the front low reference circuits of the wheel speed sensors. This step checks for a short to voltage in these low reference circuits in the front wheel speed sensors.

1. The module which was not communicating due to an open in the serial data circuit may have set Lost Communication DTCs for those modules that it was monitoring.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Data Link Connector Schematics
1 | Test the following circuits of the EBCM for an open or a short to ground.

• | Battery positive voltage inputs

• | Switched battery positive voltage inputs

• | Ignition inputs

• | Ignition outputs

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 2

2 | Test the ground circuits of the EBCM for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 3
3 |

1. Disconnect the scan tool
2. Turn the ignition ON with the engine OFF.
3. Test the UART circuit for a short to voltage.
4. Turn the ignition OFF.
5. Test the UART circuit for and open or short to ground.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4 | Inspect for poor connections/terminal tension at the following EBCM circuits:

• | Battery voltage inputs

• | Switched battery positive voltage inputs

• | Ignition inputs

• | Ignition outputs

• | Ground

• | UART data line

Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5 |

1. Turn the ignition ON with engine OFF.
2. Test the low reference circuits of both front wheel speed sensors for a short to voltage.

Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6 | Replace the EBCM . Refer to Electronic Brake Control Module Replacement in Antilock Brake System. Did you complete the replacement? | System OK | --
7 |

1. Connect a scan tool.
2. Turn ON the ignition leaving the engine OFF.
3. Select the Display DTCs function for the EBCM.

Does the scan tool display any DTCs which do not begin with a "U"?

Go to the appropriate Diagnostic System Check

Go to Step 8

8 |

1. Use the scan tool in order to clear the DTCs
2. Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared.

Did you complete the action?

System OK

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