B2960
Security System Sensor Data Incorrect But Valid
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Code B2960 is a General Motors manufacturer-specific code indicating that the Passlock security system is receiving sensor data that is technically valid (within the readable range) but does not match the expected values stored in the Body Control Module (BCM). The Passlock system uses a resistive sensor in the ignition lock cylinder to verify that the correct key is being used to start the vehicle.
When the BCM detects a mismatch between the expected and actual resistance values, it disables the fuel injectors to prevent the engine from starting—this is the anti-theft function working as designed, but being triggered incorrectly. You'll typically see the security light flashing, and the engine will either crank without starting or start and stall within seconds. This condition may be intermittent, working fine sometimes and refusing to start other times.
A common temporary fix is the Passlock relearn procedure: turn the key to the 'ON' position (don't crank), wait 10 minutes until the security light stops flashing, turn the key off for 5 seconds, and repeat this process three times. Then attempt to start the vehicle. If this works, the BCM has relearned the current sensor value. For a permanent fix, the ignition lock cylinder and Passlock sensor assembly may need replacement, or a Passlock bypass module can be installed. Professional repair typically costs $150–$600 depending on the approach taken.
Severity
Symptoms
- •Security or theft indicator light flashing on dashboard
- •Engine cranks but will not start
- •Engine starts then stalls within a few seconds
- •Intermittent no-start conditions
- •Vehicle may start normally sometimes and refuse other times
- •Key may not be recognized despite being the correct key
Likely Causes
The Passlock sensor embedded in the ignition lock cylinder measures a specific resistance value when the key turns. A degraded sensor produces incorrect resistance readings that don't match the learned value in the BCM.
Mechanical wear in the ignition lock cylinder can affect how the Passlock sensor is actuated, causing it to generate resistance values outside the expected range for the programmed key.
The wiring from the Passlock sensor to the Body Control Module can develop intermittent resistance changes from corrosion, loose connections, or chafed insulation, causing the BCM to receive incorrect but technically valid sensor data.
The BCM stores the learned Passlock resistance value and compares it to the sensor reading. A BCM with corrupted memory or failed input circuitry can misinterpret correct sensor data as incorrect.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Perform the Passlock relearn procedure (10-minute key-on reset)
- Replace the ignition lock cylinder with integrated Passlock sensor
- Inspect and repair wiring between the Passlock sensor and BCM
- Replace or reprogram the Body Control Module
- Install a Passlock bypass module to eliminate the security issue