For 1990-2009 cars

### Circuit Description

When the ignition switch is turned ON, the electronic suspension control (ESC) module monitors communications between its internal microprocessors and performs self-diagnostic tests. If an internal malfunction is detected, the ESC module will store a DTC C0550 in its memory.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0550: Electronic Control Unit (ECU) Performance

This vehicle has DTCs which include DTC symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC Symptom | DTC Symptom Descriptor
--- | ---
31 | General Checksum Failure
32 | General Memory Failure
38 | Supervision Software Failure
39 | Internal Electric Failure/Discard

### Conditions for Running the DTC

Turn the ignition ON.

### Conditions for Setting the DTC

• | The ESC Module detected on internal malfunction.

• | The malfunction must be detected when the ignition switch is first turned ON.

### Action Taken When the DTC Sets

• | Stores a DTC C0550 in the ESC memory

• | Disable all functionality

• | Sends a message to the instrument panel cluster (ICP) to display the SERVICE SUSPENSION SYSTEM message

### Conditions for Clearing the DTC

• | Under all fault conditions, the ignition must be cycled before this DTC can change from current to history.

• | The ESC module no longer detects any internal malfunctions when the ignition is first turned to the ON position

• | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

• | Use the IPC clearing DTC feature.

• | Use a scan tool.

### Diagnostic Aids

• | Since DTC C0550 is an internal malfunction to the ESC module, there is no repair procedure and the ESC module must be replaced.

• | The ESC module test for multiple internal malfunctions and will store a DTC C0550 if one or more internal malfunctions are detected. Therefore, depending on which malfunction was detected, and what internal circuitry was affected, this DTC may cause various symptoms.

### Test Description

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

1. This DTC requires ESC module replacement.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Electronic Suspension Control Schematics Connector End View Reference: Electronic Suspension Control Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Replace the electronic suspension control (ESC) module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | System OK | --