GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The vehicle content theft deterrent system is incorporated within the body control module (BCM). The BCM produces the theft deterrent fuel enable signal based on input from the door lock cylinders, the shock sensor, and the rear compartment lock cylinder. The PCM monitors the fuel enable signal during crank. If the proper signal is present on the theft deterrent fuel enable circuit, the PCM enables fuel delivery in order to allow the engine to start. . A problem that affects the inputs to the BCM will also result in a missing or an incorrect fuel enable signal to the PCM. The engine will not start as long as either condition is present. If the PCM detects that the fuel enable signal is not present or is incorrect while an attempt is made to start the engine, DTC P1629 will set

Conditions for Running the DTC

    • DTC P1626 is not present.
    • An attempt is made to start the engine.

Conditions for Setting the DTC

    • The PCM detects an incorrect signal on the theft deterrent fuel enable circuit.
    • The above condition is present for more than 2 seconds.

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

An intermittent may be caused by a poor connection, by rubbed-through wire insulation, or by a broken wire inside the insulation. Inspect for the following conditions:

Many situations may lead to an intermittent condition. Perform each inspection or test as directed.

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

    • Loose terminal connection
       -  Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.
       -  Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.
    • Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.
    •  Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.

Test Description

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

  1. Verifies the condition for setting code P1626 or P1629 is current.

  2. Verifies the condition for setting code B2955 or B2960 is current.

  3. Verifies the VTD module has sent the fuel enable password.

  4. Test the pulled high voltage is present at the theft deterrent controller (VTD) module.

  5. Test the frequency is present at the powertrain control module (PCM).

  6. If the module is replaced the new module has to be programmed.

  7. If the module is replaced the new module has to be programmed.

Step

Action

Value(s)

Yes

No

Schematic Reference: Theft Deterrent System Schematics

1

Did you perform the Powertrain On Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P1626 or P1629 set as a current code?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

Is code B2955 or B2960 set as current code?

--

Got to Diagnostic Trouble Code (DTC) List/Type

Go to Step 4

4

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the theft deterrent fuel enable parameter in the Theft Deterrent Controller (VTD) Module data list.

Does the scan tool indicate that the theft deterrent fuel enable parameter is active?

--

Go to Step 5

Go to Step 8

5

  1. Turn OFF the ignition.
  2. Disconnect the VTD module.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the theft deterrent fuel control circuit of the VTD module connector to a good ground.

Does the voltage measure near the specified value?

5V

Go to Step 6

Go to Step 7

6

  1. Turn OFF the ignition.
  2. Reconnect the VTD Module.
  3. Disconnect the Powertrain Control Module (PCM).
  4. Turn ON the ignition, with the engine OFF.
  5. With the DMM, measure the frequency from the fuel enable control circuit of the PCM connector to a good ground.

Does the frequency measure near the specified value?

50 Hz

Go to Step 12

Go to Step 8

7

Test the theft deterrent fuel enable signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the VTD module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the Powertrain Control Module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Important: Perform the Programming Theft Deterrent Components. Refer to Programming Theft Deterrent System Components .

Replace the VTD module. Refer to Ignition Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt.

Did you complete the replacement?

--

Go to Step 12

--

11

Important: Perform the Programming Theft Deterrent System Components. Refer to Programming Theft Deterrent System Components

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls - 3.1 L or Powertrain Control Module Replacement/Programming in Engine Controls - 3.8 L.

Did you complete the replacement?

--

Go to Step 12

--

12

  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