For 1990-2009 cars

### Circuit Description

The electronic brake control module (EBCM) detects an internal malfunction or loss of ground.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0550 Electronic Control Unit (ECU) Performance

### Conditions for Running the DTC

The ignition switch is in the ON position.

### Conditions for Setting the DTC

• | An internal EBCM malfunction exists.

• | System voltage is less than half the ignition voltage continuously for 0.04 seconds.

### Action Taken When the DTC Sets

If equipped, the following actions occur:

• | The ABS/ACC/DRP/EDC/IVC/TPM/VES/VSES are disabled.

• | TCS is degraded.

• | The ABS/TCS indicators turn ON.

• | The red brake warning indicator turns ON.

The DIC displays the following:

• | Service ABS

• | Service Traction System

• | Service StabiliTrak

• | Service Radar Cruise

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

• | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### Diagnostic Aids

Possible causes of this DTC:

• | Open ground at the EBCM

• | Internal EBCM malfunction

### Test Description

The number below refers to the step number on the diagnostic table.

1. Tests for a proper ground to the EBCM.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Test both of the ground circuits of the electronic brake control module (EBCM) for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 3
3 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 4
4 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 5 | --
5 |

1. Use the scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK