GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Each time the ignition cycles from OFF to ON, the radio receives VIN data over the class 2 communication circuit. If the VIN data in the radio memory matches the VIN data the radio receives over the class 2 communication circuit, the radio will operate normally.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1780 Seat Motor 4 Circuit

Conditions for Running the DTC

    • The DTC is run when the radio is turned from OFF to ON.
    • Battery voltage is between 9-16 volts.

Conditions for Setting the DTC

Installing a radio from another vehicle or installing a new body control module (BCM) and not entering the correct VIN information with the scan tool.

Action Taken When the DTC Sets

The radio does not function. The radio displays "LOC" .

Conditions for Clearing the DTC

    • When installing a radio from another vehicle of the same platform, clear the VIN data using the scan tool.
    • Installing a new BCM setup properly with the correct VIN for that vehicle.

The DTC status will turn to history when the above criteria is met. The scan tool can now clear the history DTC or the scan tool will clear automatically after 100 consecutive fault free ignition cycles.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Clear all DTCs and radio theft information. Cycle the ignition in order for the radio to learn the VIN.

  2. Clear all DTCs after the repair procedure is complete.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Use the scan tool in order to clear the DTCs.
  3. With the scan tool clear the radio theft information.
  4. Turn OFF the ignition.
  5. Turn ON the ignition, with the engine OFF.

Does the DTC Reset?

Go to Step 3

System OK

3

Replace the radio. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

System OK

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