🚨 Diagnostic Profile
Vehicle Make: Buick
Technical Description: Theft Deterrent System No Password Received
This fault indicates that the Body Control Module (BCM) or Powertrain Control Module (PCM) did not receive the correct password/key signal from the Passlock or PK3 (Passkey III) theft deterrent system during the ignition cycle. This is commonly triggered by a faulty ignition lock cylinder sensor, a failing BCM, corroded wiring at the steering column connector, or a weak/miscoded key transponder. When this error occurs, the vehicle typically enters a fuel/spark disable mode to prevent unauthorized starting, resulting in a no-start or intermittent stall condition.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a capable scan tool with bi-directional control to read Passlock sensor data and theft deterrent status codes (such as B2960, B2961, or B2963). While the physical repair (wiring, lock cylinder sensor replacement) is mechanically straightforward, accurately diagnosing whether the fault lies in the BCM, the ignition lock cylinder, or wiring harness requires intermediate electrical diagnostic skill and the ability to interpret live sensor voltage data. No airbag or restraint systems are involved, keeping this out of the “Professional Only” high-liability category, but basic multimeter proficiency and patience with the 10-minute relearn procedure are necessary.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the steering column wiring harness connector near the ignition lock cylinder for corrosion, chafing, or loose pins — this is the most common failure point. Check the battery voltage and ensure it is above 12.4V, as low voltage can falsely trigger theft deterrent faults. Inspect the key itself for visible damage to the transponder chip embedded in the plastic head. Also check for aftermarket remote start installations, which frequently interfere with the Passlock circuit.
Step 2: Diagnostic Verification
Connect a scan tool capable of reading BCM and PCM data streams. Pull stored DTCs and record any Passlock-specific codes (B2960–B2963 range). With the key in the “ON” position, monitor live Passlock sensor voltage — a healthy signal typically fluctuates between 0.9V and 4.5V smoothly when the key is turned; an erratic or flat-lined voltage indicates a failed sensor or wiring fault. Use a digital multimeter to backprobe the Passlock sensor circuit at the connector if scan tool data is inconclusive, checking for continuity and proper ground reference.
Step 3: Resolution & Reset Process
If the Passlock sensor is confirmed faulty, replace the ignition lock cylinder sensor assembly. If wiring corrosion is found, repair or replace the damaged harness section with proper weatherproof connectors. Once repairs are complete, perform the Passlock relearn procedure: turn the key to “ON” (not start) and wait for the security light to illuminate steadily, then turn OFF for 10 minutes while leaving the key in the ON-adjacent position as specified by GM procedure. Repeat this cycle up to three times if needed until the security light stops flashing and the vehicle starts normally. Clear DTCs with the scan tool and perform a test drive to confirm the fault does not return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Ignition lock cylinder/Passlock sensor, steering column wiring harness pigtail (if damaged), replacement transponder key (if applicable), GM-capable scan tool with bi-directional BCM/PCM access (e.g., Tech 2 or equivalent aftermarket tool).
Average Component Price: $45–$120 for the Passlock sensor; $15–$40 for wiring harness pigtail repair kits; $80–$150 for a replacement transponder key; dealer theft deterrent relearn/programming (if BCM replacement is needed) typically ranges $100–$250 in software/programming fees.
Estimated Labor Hours: 1.0–2.5 hours for diagnosis and sensor replacement; add 0.5–1.0 hour if the 10-minute (or 3-cycle, up to 30-minute) relearn procedure is required; BCM replacement and full theft deterrent reprogramming can extend total labor to 3.0–4.0 hours.