When a cruise control function switch is activated, the body control module (BCM) detects a predetermined voltage signal. The BCM sends a GMLAN serial data message to the engine control module (ECM) indicating the function that has been requested.
This diagnostic procedure supports the following DTC:
DTC P0575 Cruise Control Switch Signal Circuit
The engine is ON.
| • | The ECM receives an invalid cruise control switch status GMLAN serial data message from the BCM. | 
| • | This diagnostic runs continuously. | 
| • | The Cruise Control System is disabled. | 
| • | The ECM stores the DTC information into memory when the diagnostic runs and fails. | 
| • | The malfunction indicator lamp (MIL) will not illuminate. | 
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. | 
| • | All cruise control function switches are set to OFF. | 
| • | A last test failed, or the current DTC, clears when the diagnostic runs and does not fail. | 
| • | A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic. | 
| • | Use the scan tool in order to clear the DTC. | 
| • | This DTC may be stored as a history DTC without affecting the operation of the BCM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM. | 
| • | If this DTC is retrieved as both a current and history DTC, replace the BCM. | 
Step  | Action  | Yes  | No  | 
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Data Communication Connector End Views  | |||
1  | Did you perform the Diagnostic System Check - Vehicle?  | Go to Step 2  | |
2  | Is DTC P0575 current in the engine control module (ECM)?  | Go to Step 3  | Go to Diagnostic Aids  | 
3  | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?  | Go to Step 4  | --  | 
4  | 
 Does the DTC reset?  | Go to Step 2  | System OK  |