When the ignition switch is turned ON, the 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.
The ignition ON.
| • | The ESC module detected an internal malfunction. | 
| • | The malfunction must be detected when the ignition switch is first turned ON. | 
| • | Stores a DTC C0550 in the ESC memory | 
| • | Depending on which internal circuitry was affected by this malfunction, the ESC module will command one of the following actions: | 
| - | Command 0% PWM duty cycle in order to disable all four shock absorber solenoids. | 
| - | Ignore the steering position input. | 
| - | Provide shock absorber solenoid control based on the vehicle speed only. | 
| - | Sends a message to the IPC to display the SERVICE RIDE CONTROL message. | 
| - | Sends a message to the IPC to display the SHOCKS INOPERATIVE message. | 
| • | If the disable all four shock absorber solenoids action was taken, the ESC module sends a message to the PCM to limit the speed. The PCM then sends a message to the IPC to display the MAXIMUM SPEED 129 km/h (80 mph) message. | 
| • | 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. | 
| • | Using a scan tool. | 
| • | 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 tests 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. | 
The number below refers to the step number on the diagnostic table.
Step  | Action  | Yes  | No  | 
|---|---|---|---|
Schematic Reference: Suspension Controls Schematics Connector End View Reference: Suspension Controls Connector End Views  | |||
1  | Did you perform the Diagnostic System Check - Vehicle in Vehicle Control Systems?  | Go to Step 2  | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information  | 
| 
 Important: After replacement of the ESC module, use the scan tool to clear fault codes. If not cleared and there is still a fault present, the ignition cycle counting will mask the fault. Replace the ESC module. Refer to Electronic Suspension Control Module Replacement . Did you complete the replacement?  | System OK  | --  | |