GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Catera 🢒 DTC 🢒 DTC B1780 Theft Lock Enabled

Circuit Description

Theft protection ON mode is active when a valid vehicle identification number (VIN) has been stored in the radio and the last reported VIN matches. Any time the VIN is reported it is compared to the stored VIN.

Conditions for Setting the DTC
    • DTC B1780 will set when a valid VIN stored in the radio and the last reported VIN does not match.
    • DTC B1780 will also set when a valid VIN stored in the radio and no VIN reported since battery power was restored to the radio.

Action Taken When the DTC Sets
    • Stores a DTC B1780 in the IRC memory.
    • The radio displays THEFTLOCK ACTIVE when the radio is turned On.
    • All radio functions are disabled.

Conditions for Clearing the DTC
    • DTC B1780 will automatically clear when the IRC receives the correct production sequence number (the last six digits of the VIN) from the body control module (BCM) over the Class 2 serial data line.
    • Using a scan tool.

Test Description

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

  1. Clear all DTCs and cycle the ignition to check that the DTC did not falsely set.

    2.

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

Step

Action

Value(s)

Yes

No

1

Was the Radio/Audio System Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Radio/Audio System

2

  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. Turn OFF the ignition.
  5. Turn ON the ignition and check for any radio DTCs.

Is a DTC B1780 still present?

--

Go to Step 3

--

3

Select RADIO THEFT from the scan tool SPECIAL FUNCTIONS menu.

Does the radio VIN displayed match the vehicle VIN displayed?

--

Go to Step 5

Go to Step 4

4
  1. Select CLEAR THEFT and follow instructions to perform clearing procedure.
  2. Reselect RADIO THEFT.

Does the radio VIN displayed match the vehicle VIN displayed?

--

Go to Step 7

Go to Step 6

5
  1. Turn OFF the ignition.
  2. Open a door to defeat retained accessory power (if all doors were closed after you turned OFF the ignition).
  3. Turn ON the ignition.
  4. Turn the radio ON.

Is the radio still in the Theftlock mode?

--

Go to Step 6

Go to Step 7

6

Replace the radio. Refer to Radio Replacement .

Is the replacement complete?

--

Go to Step 7

--

7

  1. Turn OFF the ignition.
  2. Reassemble any connectors or components that were disconnected or removed in previous steps.
  3. Turn ON the ignition.
  4. Use the scan tool in order to clear the DTCs.

Are all DTCs cleared?

--

System OK

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