U1500

DTC U1500

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC U1500
- Inter-Device Dedicated Bus Malfunction

Circuit/System Description

DTC U1500 sets when an internal fault is detected within the vehicle communication interface module (VCIM). No external circuits are involved.

Conditions for Running the DTC

* Ignition ON.
* Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The VCIM runs the program to detect an internal faults during module power up and every 10 seconds thereafter until the module re-enters the sleep mode.

Action Taken When the DTC Sets

* The OnStar(R) status LED turns red.
* The vehicle is unable to connect to the OnStar(R) Call Center.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

Circuit/System Testing

Ignition ON, with a scan tool, clear all DTCs and operate the audio system within the Conditions for Running the DTC.

If the DTC resets, replace the VCIM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests