B2960: How to Diagnose & Fix — Key/Immobilizer Communication Error
8 vehicles · 2 makes · $10-$800 repair
How to diagnose and fix B2960: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Pontiac Bonneville · 2000–2005
The 2000-2005 Bonneville uses GM's Passlock II immobilizer, which reads a Hall-effect sensor in the ignition lock cylinder housing rather than a chip in the key. The sensor and its hair-thin wiring at the column degrade, so the BCM sees a bad or missing signal, flashes the Security lamp, and disables the fuel injectors: the engine cranks, fires for a second, then dies, or does not fire at all. It is intermittent and worse in cold weather. Owners on the Pontiac Bonneville Club and GM Forum document the 10-minute relearn ritual (key on, wait until the security light stops flashing, three cycles) as the only way to get home; the earlier 1992-1999 cars used the different PASS-Key II resistor-pellet key and are not covered by this failure mode.
Common Symptoms
- Engine starts then dies after 1-2 seconds
- Security light flashing or steadily lit with no-start
- Cranks but no fuel delivery
- Starts normally after a 10-minute key-on wait
- Intermittent, worse in cold weather
How to Fix
Temporary: perform the 10-minute Passlock relearn (three consecutive 10-minute key-on cycles). Permanent: replace the ignition lock cylinder/Passlock sensor assembly (about $100-200 in parts, plus column disassembly) and perform the relearn; inspect the yellow/black Passlock wiring at the column connector for chafing first. Many owners instead install a Passlock bypass module. No recall.
Sources for this issue (4)
Chevrolet Impala · 2000–2005
The Passlock anti-theft system causes intermittent no-start conditions where the security light comes on and the engine is disabled. The ignition lock cylinder carries a magnet read by a Hall-effect sensor in the lock housing; when the sensor, its wiring, or the BCM connector terminals fail, the BCM detects a mismatch and fuel is locked out. The problem typically worsens progressively from occasional to daily. 225+ complaints were filed for the 2002 model year alone.
Common Symptoms
- Security/theft light flashing on dashboard
- Engine cranks but will not start
- No-start condition occurs more frequently over time
- Car starts after waiting 10+ minutes
- SECURITY telltale illuminated
How to Fix
Per GM guidance for 2000-2005 Impala, first inspect the BCM connectors for damaged or loose/unseated terminals before replacing the BCM, since many replaced BCMs test good. If the Passlock sensor in the ignition lock cylinder/housing is faulty, replace the lock cylinder/sensor assembly and perform the roughly 30-minute Passlock relearn (key on, engine off, until the security light goes out). As a temporary measure, leaving the key on until the security light stops flashing (about 10 minutes) and retrying will often start the car.
Sources for this issue (2)
Chevrolet HHR · 2006–2011
The HHR uses GM's PASS-Key III+ theft-deterrent system, which reads a transponder chip in the ignition key. A fault in this system commonly triggers a false theft condition. The 'Service Theft Deterrent System' message appears, the security light flashes, and the engine cranks but will not start (or will not crank), often intermittently. A damaged key transponder, a fault in the reader circuit, a weak battery, or poor grounds/connections are the usual culprits.
Common Symptoms
- Security/anti-theft light flashing
- 'Service Theft Deterrent System' message
- Engine cranks but won't start
- Intermittent no-start that clears after a wait
- Gauges acting erratically during the fault
How to Fix
Try a second programmed key, then the 30-minute (3-cycle) PASS-Key III+ relearn: turn key to ON without starting until the security light stops flashing, then start. If it recurs, check grounds and the theft-deterrent wiring, replace the faulty key or ignition lock cylinder/reader as diagnosed and perform the relearn; verify battery health first.
Sources for this issue (2)
Chevrolet Malibu · 2000–2005
Chevrolet Silverado 1500 · 1999–2007
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B2960 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B2960 mean?
B2960 stands for "Key/Immobilizer Communication Error." B2960 is a body/security code indicating a key or immobilizer (anti-theft) communication error, where the security module read sensor or key data that appears valid in form but does not match the expected, previously learned value. On many vehicles this involves a Passlock or transponder/immobilizer check that must pass before the computer allows the engine to start. When it fails, you typically get a security/anti-theft warning light and a no-start or no-crank condition. This is a manufacturer-specific code tied to the theft-deterrent system rather than an engine mechanical fault.
What are the most common causes of B2960?
The most common causes of B2960 are: Faulty Passlock/ignition lock cylinder sensor, Damaged or worn transponder key or key chip, Wiring or connector fault in the security sensor circuit, Body control module (BCM) failure or needs relearn, Incomplete or lost immobilizer/key relearn procedure, Worn ignition lock cylinder, Aftermarket alarm or remote-start interference. The specific cause varies by vehicle.
How much does it cost to fix B2960?
Repair costs for B2960 range from $10 to $800, depending on the vehicle and root cause.
Which vehicles are affected by B2960?
Au7o has documented B2960 across 8 vehicle models from 2 manufacturers: Chevrolet, Pontiac.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.