🚨 Diagnostic Profile
Vehicle Make: BUICK
Technical Description: Theft Deterrent System Password Incorrect
This fault indicates that the Body Control Module (BCM) or theft deterrent module received an incorrect password/key signal from the ignition key or related security module (PASS-Key/PATS-equivalent system). This typically prevents the vehicle from starting as the Powertrain Control Module (PCM) does not receive authorization to enable fuel and ignition systems.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a diagnostic scan tool capable of reading security/theft deterrent system data, along with knowledge of resistance-pellet key systems or transponder-based security circuits. While not as high-liability as airbag/restraint repairs, it does require careful handling of security relearn procedures and may require dealer-level programming tools (such as GM Tech2 or GM MDI with Techline software) in more advanced cases.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the ignition lock cylinder wiring harness for corrosion, loose pins, or chafed wires. Check the connector at the base of the ignition switch and the BCM harness connector for secure, clean contacts. Inspect the key itself for a damaged, worn, or missing resistor pellet (on older systems) or a cracked transponder chip (on newer systems). Confirm that the battery voltage is within normal range (12.4V-12.8V at rest) since low voltage can cause false theft deterrent faults.
Step 2: Diagnostic Verification
Connect a scan tool capable of accessing the Body Control Module and Theft Deterrent System data stream. Check for stored DTCs such as B2960 (Password Incorrect), B2900s, or related security codes. Use a digital multimeter to test resistance across the ignition key pellet circuit (should typically read a specific resistance value per GM specifications, often between 0 and 15,000 ohms depending on the key code). Verify communication between the BCM and PCM to ensure the security data bus (Class 2 / GMLAN) is transmitting correctly without interference or intermittent dropouts.
Step 3: Resolution & Reset Process
If the key pellet or transponder is damaged, replace the key with a correctly coded replacement. If the ignition lock cylinder or wiring harness is faulty, repair or replace as needed. After replacing components, perform the Theft Deterrent System relearn procedure: turn the ignition to the ‘ON’ position (engine off) and wait approximately 10 minutes for the Security Indicator light to turn off, signaling the system has relearned the key. If the system does not reset, it may require dealer-level reprogramming using GM Tech2/MDI software to reset the Password Incorrect fault and resynchronize the BCM with the PCM.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Replacement ignition key with resistor pellet or transponder chip, ignition lock cylinder (if worn), BCM connector repair kit, GM Tech2/MDI diagnostic and programming tool (shop-level, not consumer).
Average Component Price: $15–$40 for a replacement key (pellet-style), $80–$150 for a transponder-based key, $150–$350 for an ignition lock cylinder, and $75–$150 in dealer programming fees if BCM relearn/reset is required.
Estimated Labor Hours: 0.5 to 1.5 hours for diagnostic testing and key relearn procedures; 1.5 to 2.5 hours if ignition lock cylinder replacement or wiring harness repair is necessary.