GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The theft deterrent module (TDM) produces the theft deterrent fuel enable password when the ignition is ON and the proper transponder key value is detected. The powertrain control module (PCM) monitors the fuel enable password. If the proper signal is present on the serial data circuit, the PCM enables the fuel delivery in order to allow the engine to start. If the PCM determines that the fuel enable password is not present or incorrect while the engine is running, the PCM will enter a fail enable state. The engine will not stall or stop running. If the PCM is fail enable, the PASS-Key III Plus system is NOT active and the engine will start. Refer to Immobilizer Description and Operation .

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1626 Theft Deterrent Fuel Enable Signal Lost

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The PCM has either lost or not received the password from the theft deterrent control module.

Action Taken When the DTC Sets

    • The vehicle will not start.
    • The PCM sends a serial data message to the body control module (BCM) to illuminate the SECURITY indicator.
    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

Refer to Testing for Intermittent Conditions and Poor Connections and Testing for Electrical Intermittents .

Test Description

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

  1. To set this code, the password that the PCM has learned does not agree with the password being received from the theft deterrent control module. This condition can occur if the theft deterrent control module has been replaced and the programming theft deterrent system components procedure has not been performed.

  2. If the PCM resets the DTC after the programming theft deterrent system components procedure has been performed, the theft deterrent control module is malfunctioning.

Step

Action

Yes

No

Schematic Reference: Immobilizer Schematics

Connector End View Reference: Immobilizer Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: If a 10-Minute Re-Learn Procedure or a 30-Minute Re-Learn Procedure is performed, all keys not learned at that time will be erased and will not be recognized. Perform the Adding Keys procedure on all keys or instruct the customer how to perform the Adding Keys procedure. Refer to Adding Keys .

Perform the Programming Theft Deterrent System Components procedure. Refer to Immobilizer System Component Programming .

Is the procedure complete?

Go to Step 3

--

3

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 4

System OK

4

Important: If a 10-Minute or 30-Minute Re-Learn Procedure is performed, all keys not learned at that time will be erased and will not be recognized. Perform the Adding Keys procedure on all keys or instruct the customer how to perform the Adding Keys procedure. Refer to Adding Keys .

    • If original vehicle keys are to be reused, perform the theft deterrent module (TDM) setup prior to TDM replacement. Refer to Immobilizer System Component Programming .
    • If new vehicle keys are being used, performing the TDM setup prior to TDM replacement is not required.

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

Did you complete the replacement?

Go to Step 5

--

5

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK