Circuit Description
This vehicle utilizes both a Class 2 and Entertainment and Comfort Serial Data line for communication with the OnStar® Vehicle Communication Interface Module (VCIM). Class 2 messaging is utilized for inter-module information transfer to support features such as remote door locking and unlocking. Because this vehicle does not utilize a Class 2 supported radio, the E & C data line must be implemented to transfer the OnStar® audio signals from the VCIM to the vehicle audio system. In the event the Entertainment and Comfort Serial Data line is shorted to ground, shorted to voltage or opened , U1306 is set as current and can be read through the use of the scan tool over the Class 2 Serial Data line. Calls will still be placed to the OnStar® Call Center if a keypress is make, however, no OnStar® audio will be heard and the radio will not mute if currently turned on.
Conditions for Running the DTC
| • | The ignition must be in the RUN or ACC position, or retained accessory power (RAP) must be active. |
| • | The system voltage is at least 9.5 volts and no more than 15.5 volts. |
| • | All of the above conditions are present for greater than 300 ms. |
Action Taken When the DTC Sets
| • | The VCIM does not communicate with the radio. |
| • | No OnStar® audio is heard and the radio will not mute after a keypress is made. |
| • | The OnStar® status LED turns Red. |
Conditions for Clearing the MIL/DTC
| • | The VCIM does not detect a short to ground on the Entertainment and Comfort Serial Data Bus |
| • | The VCIM does not detect a short to voltage on the Entertainment and Comfort Serial Data Bus |
| • | The VCIM does not detect an open in the Entertainment and Comfort Serial Data Bus |
| • | A history DTC clears after 50 malfunction free ignitions cycles |
| • | The VCIM detects the clear DTC command from the scan tool |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Data Link Connector Schematics | ||||
1 | Did you perform the Cellular Communication Diagnostic System Check? | Go to Step 2 | ||
2 |
Important: The scan tool must be disconnected from the DLC to perform this step.
Does the voltage measure greater than the specified value? | 0 V | Go to Step 3 | Go to Step 4 |
3 | Test the Entertainment and Comfort Serial Data circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | |
4 | Test the Entertainment and Comfort Serial Data circuit for an open or short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 | |
5 |
Are the minimum and maximum voltages measured near the specified range? | Min 0.76 V-Max 10.0 V | Go to Step 8 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the radio and VCIM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | |
7 | Replace the radio. Refer to Radio Replacement in Entertainment. Did you complete the replacement? | Go to Step 9 | -- | |
8 |
Important: Perform the OnStar® setup procedure. Replace the Vehicle Communication Interface Module. Refer to Communication Interface Module Replacement . Did you complete the replacement? | Go to Step 9 | -- | |
9 |
Does the DTC reset? | Go to Step 2 | System OK | |
