B2960 on Chevrolet: How to Diagnose & Fix
Key/Immobilizer Communication Error
6 Chevrolet models · 6 documented issues · 1 critical · $10-$800 repair
B2960 on Chevrolet by model: symptoms, diagnosis and fix
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)
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)
A common failure on early-2000s Malibu models is the Passlock security system falsely detecting a theft condition, which can disable fuel delivery and prevent the engine from starting. Owners report the SECURITY light flashing, long wait times before restart, and in some cases intermittent stalling or crank-no-start behavior. The root cause is typically failure in the ignition lock cylinder sensor/housing or related wiring causing incorrect resistance/voltage readings to the body control module.
Common Symptoms
- SECURITY light flashing or staying on
- Crank but no start
- Starts after waiting 10 minutes
- Intermittent stalling
- No injector pulse/fuel disable
- Random no-start especially in hot weather
How to Fix
Diagnosis usually starts by checking for SECURITY lamp behavior, BCM-related codes, and verifying Passlock sensor data during crank. Repairs commonly involve replacing the ignition lock cylinder housing/switch assembly, repairing wiring at the column, and performing the Passlock relearn procedure. Some owners also replace the ignition switch if heat-related internal contact failure is present.
Sources for this issue (2)
The Passlock II theft-deterrent system reads a Hall-effect sensor and magnet in the ignition lock cylinder. As the sensor or lock cylinder wears, the BCM sees an out-of-range voltage, flags a theft fault, flashes the SECURITY light, and disables fuel injection so the engine cranks but won't start. Owners get stranded with a 'Service Theft System' or security light and a no-start that often clears after a wait.
Common Symptoms
- Engine cranks but will not start
- SECURITY / 'Service Theft System' light flashing or lit
- No-start clears after waiting ~10 minutes
- Intermittent stalling just after start
- Theft codes stored in BCM
How to Fix
First try the 10-minute relearn: key to ON, attempt start, then leave key ON until the security light stops flashing (~10 min), key off 5 sec, then start; repeat up to 3 cycles. If it recurs, replace the Passlock sensor or ignition lock cylinder and relearn.
Sources for this issue (3)
First-generation Colorado/Canyon trucks commonly suffer from Passlock-related ignition switch failures that trigger a crank-no-start or start-and-stall condition with the security light illuminated. Owners often report the truck starting normally after a 10-minute relearn wait, then failing again later. GM issued service information on theft deterrent and ignition switch diagnosis, and the issue is widely documented in owner complaints and forums.
Common Symptoms
- crank no start
- starts then stalls
- security light on
- intermittent no start
- must wait 10 minutes before restart
- no injector pulse
How to Fix
Diagnosis includes checking for theft deterrent codes, monitoring the security indicator, and verifying ignition switch/Passlock sensor operation. The usual fix is replacing the ignition switch assembly and performing the relearn procedure; some owners also inspect wiring at the column and battery voltage because low voltage can aggravate the system. If repeated failures continue, the lock cylinder housing and related wiring should be inspected.
Sources for this issue (3)
The Passlock security system frequently malfunctions, reading the wrong resistance from the ignition cylinder sensor and refusing to allow the engine to start. The security light flashes and the car cranks but will not fire. This commonly occurs in cold weather or after the ignition cylinder wears internally.
Common Symptoms
- Engine cranks but will not start
- Security light flashing on dash
- Intermittent no-start condition
- Problem worse in cold weather
How to Fix
The temporary fix is to turn the key to ON (not start), wait 10 minutes for the security light to stop flashing, then turn off and restart. The permanent fix is to bypass the Passlock sensor by wiring a 2.2K ohm resistor in place of the hall-effect sensor in the ignition cylinder. Some owners replace the entire ignition lock cylinder assembly.
Sources for this issue (1)
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 on a Chevrolet?
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. On Chevrolet it is documented across 6 models: Impala, HHR, Malibu, Silverado 1500, Colorado, Cavalier.
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 on a Chevrolet?
Published repair estimates on Chevrolet range from $10 to $800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for B2960 on a different make?
View B2960 across all makes →Join 700+ subscribers following Au7o for vehicle insights and updates.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.