GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The powertrain control module (PCM) monitors the state of health message from the theft deterrent system to ensure that the PCM to theft deterrent module communication is established. If the PCM detects a loss of the state of health message while the engine is running, DTC P1626 will be set. DTC P1626 can cause a no-start condition or normal operation depending upon when the loss of theft deterrent system communication was detected. The engine will continue to start and run if the condition that set DTC P1626 occurred after the PCM received a valid theft deterrent password from the theft deterrent module and already allowed fuel during the ignition cycle. The engine will not start if the condition that set DTC P1626 occurred before the PCM received a password. With this condition present, the PCM will inhibit fuel delivery and disable the starter until a valid password is detected. Refer to Vehicle Theft Deterrent (VTD)Circuit Description in Theft Deterrent.

Conditions for Running the DTC

The ignition is on.

Conditions for Setting the DTC

The PCM has detected a loss of the state of health message from the theft deterrent system.

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

Inspect for the following conditions:

Step

Action

Values

Yes

No

1

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

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Go to Step 2

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2

Important: :  If a loss of DLC data has already been diagnosed, clear this DTC and continue diagnosis with .

Is P1631, or UXXXX DTCs present?

--

Go to applicable DTC

Go to Step 3

3

Important: : The replacement PCM must be programmed.

Replace the PCM. Refer to .

Did you complete the replacement?

--

Go to Step 4

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4

  1. Review and record scan tool Fail Records data.
  2. Clear DTCs.
  3. Attempt to start the vehicle.

Does the vehicle start and continue to run?

--

Go to Step 2

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