U1500

Diagnostic Chart:

SCHEMATIC
Refer to OnStar(R) Schematics for DTC U1500 schematic information.

CIRCUIT DESCRIPTION
The DTC U1500 is set when the VIU detects no communication between the VIU and the Vehicle Communication Unit (VCU).

CONDITIONS FOR RUNNING THE DTC
^ The ignition must be in the RUN or ACC position.
^ The VIU will run this test every 300 ms.
^ Battery voltage must be greater than 9.5 volts.
^ Battery voltage must be less than 15.5 volts.

ACTION TAKEN WHEN THE DTC SETS
When DTC U1500 is current the VIU does not communicate with the VCU. No calls can be placed.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The code can be cleared with the scan tool when the VIU does not detect a failure during the last diagnostic cycle.
^ The history code will clear after 50 Key cycles without the code present.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step test for proper operation of the OnStar(R) system.
4. This step tests for an open in the battery positive circuit between the VIU and the VCU.
5. This step tests for an open or a short to battery positive.
7. This step tests for an open or a short to battery positive.