DTC B3935. Buick Regal 2009

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2009 🢒 Regal 🢒 DTC 🢒 DTC B3935

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3935 00: Transponder Authentication Error

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 body control module (BCM). The BCM then compares this value to a value stored in memory. If the value is not correct, the BCM disables an engine start.

Conditions for Running the DTC

•	Ignition is in the Accessory or Run position.

•	A valid transponder value has been read.

Conditions for Setting the DTC

•	The transponder value is valid and matches the value stored in the BCM memory.

•	The transponder calculation of the challenge from the BCM does not match the BCM calculation.

Action Taken When the DTC Sets

•	Vehicle starting will be disabled.

•	The security indicator in the instrument cluster will be illuminated. The driver information center will display a service message.

Conditions for Clearing the DTC

•	A current DTC will be cleared when a valid transponder value has been read and authenticated.

•	A history DTC will be cleared after 100 malfunction-free ignition cycles or when a scan tool is used to clear DTCs.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Replace the suspected inoperative or malfunctioning key. DTC B3935 should not reset and the vehicle should start.

⇒	If the replacement key results in the resetting of DTC B3935, replace the K9 Body Control Module (BCM).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Replacing Keys

•	Control Module References for BCM replacement, setup, and programming