B2476 - Cellular Phone Select Service Switch Malfunction

Diagnostic Chart:

SCHEMATIC
Refer to OnStar(R) Schematics for three button assembly schematic information.

CIRCUIT DESCRIPTION
If the voltage received from the three button assembly to the Vehicle Interface Unit (VIU) is not between a predescribed high and low limit then the VIU will set the DTC.

CONDITIONS FOR RUNNING THE DTC
^ The ignition must be in the RUN or ACC position.
^ The VIU will test for the reference voltage from the three button assembly every 300 ms during VIU power on.

and the VIU power must be on.

CONDITIONS FOR SETTING THE DTC
^ The signal voltage received by the VIU is greater than 2.8 volts.
^ The signal voltage received by the VIU is less than 3.2 volts.

ACTION TAKEN WHEN THE DTC SETS
When the code is current the VIU will ignore all inputs from the OnStar(R) Button Assembly.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The code can be cleared when the VIU does not detect a failure during the last diagnostic cycle.
^ The code will clear from history after 50 ignition cycles with no code present.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step inspects the circuits of the three button assembly for shorts, opens and continuity.
4. This step verifies the operation of the three button assembly through the Tech 2.
7. Using the Tech 2, verify the repair was complete.