GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 CTS 🢒 DTC 🢒 DTC B3935

Circuit Description

When an ignition key is inserted into the ignition lock cylinder and the ignition is switched 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 theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory, learned key code. If the value is correct the theft deterrent control module sends a random generated number to the transponder, this is called a challenge. Both the transponder and the theft deterrent control module perform a calculation on the challenge, if the calculations match the theft deterrent control module sends the fuel enable password via the class 2 serial data circuit to the engine control module (ECM). If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable password to the ECM via the class 2 serial data circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3935 Transponder Authentication Error

Conditions for Running the DTC

The ignition switch is in the ON position and the battery voltage is greater than 9 volts.

Conditions for Setting the DTC
    • The transponder value matches the value stored in the theft deterrent control modules memory.
    • The transponders calculation on the challenge from the theft deterrent control module does not match the theft deterrent control modules calculation.

Action Taken When the DTC Sets
    • The vehicle will not start.
    • The theft deterrent control module sends a message via the serial data circuit to the radio to display STARTING DISABLED REMOVE KEY.
    • The theft deterrent control module sends a message via the serial data circuit to the instrument panel cluster (IPC) to flash the SECURITY indicator.

Conditions for Clearing the MIL/DTC
    • The theft deterrent control module clears the current status of the DTC when the transponders calculation on the challenge matches the theft deterrent control modules calculation.
    • The DTC can be cleared by using a scan tool.

Test Description

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

  1. Verifies the conditions for setting DTC B3055 or B3060 are not current.

    2.

  2. If a new key must be tried, the key must have the proper mechanical cut and the theft deterrent control module must "learn" the transponder value.

    3.

  3. If the replacement key does not work, the theft deterrent control module must be malfunctioning.

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

Is DTC B3055 or B3060 set as a current code?

Go to DTC B3055 or DTC B3060

Go to Step 3

3

Important: Two learned master keys are required to perform the Adding Keys procedure on export vehicles with option code (UA2 OR Z49)

  1. Replace the suspect key.
  2. Copy the mechanical cut of the available key on a pass key III+ (PK3+) replacement key.
  3. Perform the Adding Keys procedure if a learned master key is available. Refer to Adding Keys . If the required number of learned master keys are not available. Refer to Replacing Keys .

Did you complete the replacement?

Go to Step 4

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4

Does the replacement key cause DTC B3935 to set?

Go to Step 5

Go to Step 6

5

Important: If a 10 Minute or 30 Minute Re-Learn Procedure is perform, 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 .

Replace the theft deterrent control module. Refer to Control Module References for replacement, setup and programming.

Did you complete the replacement?

Go to Step 6

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6
  1. Use a scan tool in order to clear the DTCs.
  2. Attempt to start the vehicle.

Does the DTC reset?

Go to Step 2

System OK