GM Service Manual Online
For 1990-2009 cars only

Circuit Description

When an ignition key is inserted into the ignition lock cylinder and switch to ON, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the body control module (BCM). The BCM then compares this value to a value stored in memory, learned key code. If the value is correct the BCM sends the fuel enable password via the serial data circuit to the powertrain control module (PCM).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2945 Security System Sensor Power Circuit

Conditions for Running the DTC

The ignition is switched from ON to OFF.

Conditions for Setting the DTC

If the BCM senses the security system sensor supply circuit is short to battery positive when the ignition is in the OFF position DTC B2945 will be set as a current DTC. If the DTC is current when the ignition is switched to the ON position the DTC will become a history DTC.

Action Taken When the DTC Sets

With the ignition ON DTC B2945 can only be retrieved as a history DTC. There will be no symptom to the driver of a failure.

Conditions for Clearing the MIL/DTC

    • The BCM clears the history status of the DTC after 100 fault-free ignition cycles.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

A security system sensor supply circuit that is shorted to battery positive could cause an open in the theft deterrent exciter module which will cause DTC B3055. If you were sent to this diagnostics from DTC B3055 table ensure you complete DTC B3055 diagnostics after DTC B2945 condition has been corrected.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step verifies that DTC B2945 is current. DTC B2945 will only be set as a current DTC when the ignition OFF. To inspect for a current DTC B2945, the ignition must be first turned ON to wake up the module, then the ignition must be turned OFF to inspect for the DTC.

Step

Action

Yes

No

Schematic Reference: Theft Deterrent System Schematics

Connector End View Reference: Theft Deterrent System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn the ignition ON.
  2. Turn the ignition OFF.
  3. With a scan tool, check for current DTCs.

Is DTC B2945 set as current?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

Inspect the security system sensor supply voltage circuit for a short to battery. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections

4

  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