For 1990-2009 cars

### DTC Descriptor

DTC B3935 57 : Transponder Key Identification Error

### Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle .

### Circuit/System 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 energised by the exciter coils surrounding the ignition lock cylinder. The energised transponder transmits a signal that contains its unique value, which is received by the theft deterrent module (TDM). The TDM then compares this value to a value stored in memory. This stored value is the learned key code. If the value is correct, the TDM sends the start enable password via the serial data circuit to the engine control module (ECM). If either the transponders unique value or the calculation to the challenge is incorrect, the TDM will send the start disable password to the ECM.

### Conditions for Running the DTC

• | Ignition is in the ACC or ON position.

• | A valid transponder value has been read but not authenticated.

### Conditions for Setting the DTC

• | The transponder value is invalid or does not match the value stored in the TDM memory.

• | The transponder calculation to the challenge from the TDM does not match the TDMs calculation.

### Action Taken When the DTC Sets

• | Vehicle starting will disable.

• | The security warning lamp will illuminate.

### Conditions for Clearing the DTC

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

• | A history DTC will clear after 100 fault-free ignition cycles.

• | The DTC can be cleared using a scan tool.

### Reference Information

#### Description and Operation

Theft Systems Description and Operation

#### Scan Tool Reference

Control Module References

### Circuit/System Testing

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 TDM.

### Repair Instructions

Perform the Diagnostic Repair Verification .

• | Replacing Keys

• | Adding Keys

• | Control Module References .