This DTC indicates an internal fault and is set within the vehicle communication interface module (VCIM). No external circuits are involved.
This diagnostic procedure supports the following DTC:
DTC U1500 Inter-Device Dedicated Bus - single or 1
The microprocessor runs the program to detect an internal fault during module power up, and every 10 seconds thereafter, until the module re-enters the sleep mode.
The VCIM detects an internal communication malfunction.
• | The OnStar® status LED turns red. |
• | The vehicle is unable to connect to the OnStar® Call Center. |
• | A current DTC clears when the malfunction is no longer present. |
• | A history DTC clears after 50 malfunction-free ignition cycles. |
• | The diagnostic procedure used for DTC U1500 in OnStar® systems with single module generations of OnStar® differ greatly from previous generations with 2 modules. While these older generations denoted a failure of the 3-wire bus between the modules by setting a U1500, single module OnStar® systems use this DTC to denote an internal module failure. The determination of whether a 1 or 2 module generation of OnStar® is used should be confirmed. Refer to OnStar Description and Operation . |
• | This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the VCIM. |
• | If this DTC is retrieved as both a current and history DTC, replace the VCIM. |
Step | Action | Yes | No |
---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Is the DTC retrieved as a current DTC? | Go to Step 3 | Go to Diagnostic Aids |
3 | Replace the VCIM. Refer to Control Module References in Computer/Integrating Systems 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 |