OBD-II Code B2960: Security System Mismatch

What Does B2960 Mean?

B2960 means the GM Passlock anti-theft system received an unexpected voltage signal from the ignition lock. The signal represents an intact circuit, but its resistance value does not match the unique code stored in the Body Control Module (BCM). This mismatch triggers the BCM to disable the fuel injectors, causing a start-and-stall condition.

Technical definition: Security System Sensor Data Incorrect But Valid. The Body Control Module (BCM) reads a valid voltage from the Passlock sensor (a Hall effect sensor and resistor in the ignition cylinder), but the voltage differs from the learned baseline, prompting a fuel disable command to the Powertrain Control Module (PCM).

Can I Drive With B2960?

Yes, But With Caution. You can continue driving if the engine is already running, but the vehicle will not restart once turned off. If the fault occurs while driving, the car enters a 'fail enable' mode, indicated by a solid 'SECURITY' light, allowing it to run until the ignition cycles. The primary risk is being stranded. Repeated start-and-stall cycles drain the battery without harming mechanical components.

Common Causes

• Worn Ignition Lock Cylinder or Passlock Sensor (Very Common) — Mechanical wear on the ignition cylinder and its internal magnet causes the integrated Passlock sensor to send fluctuating voltage signals to the BCM. This is the most frequent point of failure.
• Damaged Steering Column Wiring (Common) — The three thin wires leading from the ignition lock cylinder stretch, break, or chafe inside the steering column. This alters circuit resistance and the resulting voltage read by the BCM.
• Operator Error (Rapid Key Turn) (Common) — Turning the key directly from 'Off' to 'Crank' without a momentary pause in the 'On' position causes rapid voltage fluctuations. Combined with high starter current draw, this forces the BCM to misread the Passlock voltage.
• Corroded BCM Connectors (Less Common) — Poor terminal connections at the BCM introduce voltage offsets that mimic a sensor failure. GM TSB #04-08-47-003 highlights this specific issue for 2000-2005 Impalas and Monte Carlos.
• Failing Ignition Switch (Less Common) — The electronic ignition switch wears out, delivering unstable voltage to the system during cranking. Inconsistent internal contacts trigger B2960, notably on 2003-2007 Saturn Ions.
• Weak Battery (Uncommon) — A weak battery causes severe voltage drops during cranking. This forces the BCM to incorrectly process the Passlock sensor's signal, especially if the sensor is already worn.
• Failing Body Control Module (BCM) (Rare) — The BCM loses its learned Passlock code or suffers internal solder joint failures. This requires professional diagnosis and should only be considered after ruling out wiring and sensor faults.
• Aftermarket Alarm Interference (Rare) — Improperly installed remote start or alarm systems tap into security wiring and interfere with the Passlock system's sensitive analog voltage signals.

Symptoms

• Engine starts and immediately stalls (within 1-3 seconds) — The engine fires and runs briefly, but shuts off as the BCM instructs the PCM to cut fuel delivery upon detecting the security fault.
• Flashing 'SECURITY' light on the dashboard — When a fault is detected during a start attempt, the security light flashes. This directly indicates an active Passlock system problem preventing the engine from running.
• Engine cranks but will not start — The starter turns the engine over, but it never fires because the BCM refuses to send the 'start enable' message to the PCM.
• Solid 'SECURITY' light while driving — If the fault occurs while the engine is running, the light stays on steadily. The car operates in 'fail enable' mode but will not restart after being turned off.
• Incorrect Passlock voltage reading in BCM live data (scan-tool only — no driver-felt sign) — When viewed on a scan tool, the Passlock data voltage is incorrect or the Passlock State shows 'Tamper' when the fault occurs.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace Ignition Lock Cylinder with Passlock Sensor — Parts: $100-$250, Labor: $150-$300, ~1.8 hr book time (Intermediate)
• Install a Passlock Bypass/Eliminator Module — Parts: $50-$250, Labor: $100-$200, ~1.2 hr book time (DIY)
• Repair Damaged Wiring or Clean BCM Connectors — Parts: $10-$30, Labor: $125-$250, ~2 hr book time (Intermediate)
• Replace Ignition Switch — Parts: $50-$150, Labor: $100-$250, ~1.5 hr book time (Intermediate)
• Replace Body Control Module (BCM) — Parts: $250-$600, Labor: $150-$350, ~2 hr book time (Professional)

Used vs. New Parts: Buying Guide

When a used part is worth it: For the primary fix (ignition lock cylinder with Passlock sensor), buying used rarely makes sense. This is a known high-wear component. The low cost of new aftermarket parts makes them a much safer investment.

Donor-vehicle mileage cap: roughly under 40000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Source from a very low-mileage vehicle totaled due to collision, not electrical failure.
• Verify the exact part number, as there are variations.
• Avoid parts from regions with high humidity or extreme temperatures, which accelerate wear and corrosion.

Decision logic:

• If The part is an ignition lock cylinder with a Passlock sensor → Buy a new OEM or reputable aftermarket part (e.g., ACDelco, Dorman). The risk of a used part failing is not worth the minimal cost savings.
• If The part is a BCM and budget is extremely tight → A used BCM is an option, but it MUST be professionally cloned with the data from your original BCM or it will not work.

Warranty tradeoff: Used parts typically have a 30-90 day warranty. New aftermarket parts carry a 1-year to limited lifetime warranty. OEM parts have a 12-month warranty if installed by a dealer.

Worst-case if a used part fails: $200-$400 if a used part fails after the warranty period, requiring a second repair.

What Happens If You Wait — Timeline

1. 0-1 month: Intermittent start-and-stall. Occurs once every few weeks, often triggered by cold weather. The 10-minute relearn procedure temporarily resolves it. (MPG impact: 0%% · Added cost: $0)
2. 1-3 months: Failure becomes more frequent, happening multiple times a week. The driver becomes reliant on the 10-minute trick, causing significant delays. (MPG impact: 0%% · Added cost: $75-$250 (Potential tow service if the temporary fix fails))
3. 3-6 months: The vehicle is completely unreliable. The start-and-stall happens on most start attempts. Repeated failed cranks drain and weaken the battery. (MPG impact: 0%% · Added cost: $150-$250 (Cost of a new battery from excessive draining))
4. 6+ months: The Passlock sensor or wiring fails completely. The vehicle does not start under any circumstances. The car is immobilized, incurring costs for towing. (MPG impact: 0%% · Added cost: $300-$800+ (Combines towing, battery replacement, and mandatory repair))

Cost of Not Fixing It

• Immediate: Vehicle does not start, causing driver to be stranded. This is the primary and most significant consequence. (Added cost: $75-$250 for a tow truck service.)
• 0-1 month: Intermittent no-start condition becomes more frequent and unpredictable. Drained battery from repeated, failed start attempts. (Added cost: $150-$250 for a new battery and installation.)
• 1-6 months: Complete vehicle unreliability. The cost of being stranded escalates if it occurs far from home, requiring lodging or a rental car. (Added cost: $100-$500+ for hotels, rental cars, and other transportation costs.)

Diagnosis Steps

1. Observe the 'SECURITY' Light Behavior
   Attempt to start the vehicle. A flashing light indicates an active fault preventing a start. A solid light means a fault occurred previously, but the car starts. No light indicates a different issue or a burned-out bulb.
   Tools: ['None']
2. Attempt the 30-Minute Security Relearn
   Turn the key to 'ON' (do not start) and wait for the 'SECURITY' light to stop flashing (approx. 10 minutes). Turn the key 'OFF' for 20 seconds. Repeat this process two more times for a total of three 10-minute cycles. This resynchronizes the system if the code stems from a temporary glitch.
   Tools: ['Stopwatch or timer']
3. Scan for Body (B) and Powertrain (P) Codes
   Use an OBD-II scanner capable of reading Body (B) codes to confirm B2960 is present. Check for related codes like P1631 (Theft Deterrent Start Enable Signal Not Correct) or B2958 (Data Circuit High). P1631 is a result of B2960, not a separate problem.
   Tools: ['OBD-II Scanner (BCM capable)']
4. Inspect the Ignition Cylinder Wiring Harness
   Remove the steering column shrouds and visually inspect the three-wire harness coming from the ignition lock cylinder. Look for stretching, breaks, or chafing where the wires enter the column, especially near the tilt-steering pivot.
   Tools: ['Screwdriver set', 'Trim removal tools', 'Flashlight']
5. [PRO TIP] Perform a Voltage Drop Test on the Signal Wire
   Back-probe the yellow signal wire at the ignition switch connector. With the key ON (engine off), voltage reads a steady 4.7-5.0V. As you turn the key to CRANK, this voltage drops to a specific, stable value (e.g., 2.8V). Wild fluctuations or no drop confirms a faulty Passlock sensor or wiring.
   Tools: ['Digital Multimeter', 'Back-probe pins']
6. [PRO TIP] Perform a 'Wiggle Test' at the BCM
   Locate the Body Control Module. With the key ON and a scan tool monitoring Passlock data voltage, gently wiggle the connectors at the BCM. Erratic voltage readings indicate a poor terminal connection at the module, a known issue on Chevy Impalas.
   Tools: ['OBD-II Scanner (BCM capable)']
7. Check Power and Ground at the Passlock Sensor
   Verify the Passlock sensor receives correct power. Back-probing the Red/White wire shows 9.0V or higher with the key in ON, RUN, and CRANK. The Orange/Black wire requires a solid ground connection. Improper power or ground forces the sensor to output an incorrect signal.
   Tools: ['Digital Multimeter', 'Back-probe pins']
8. [ADVANCED] Measure Passlock Sensor Resistance
   Disconnect the battery. At the Passlock sensor connector, cut the yellow signal wire and the black ground wire. Measure the resistance between the yellow and black wire ends leading into the ignition lock cylinder. The reading must correspond to one of GM's 10 master resistor values (ranging from ~500 Ω to ~13.6 kΩ). Infinite resistance confirms a failed sensor.
   Tools: ['Digital Multimeter', 'Wire cutters/strippers'] (Advanced)
9. [ADVANCED] Monitor Scan Tool Live Data PIDs
   Monitor BCM data PIDs. Watch 'Passlock Data Voltage', 'Passlock State', and 'Ignition 1/3 Voltage'. When the fault occurs, 'Passlock State' changes to 'Tamper' or 'Fail'. 'Passlock Data Voltage' shows a stable 5V KOEO and drops to a consistent voltage during crank. Fluctuations point to a sensor or wiring issue.
   Tools: ['Advanced OBD-II Scan Tool'] (Advanced)
10. [ADVANCED] Confirm Fuel Cut-Off Command
    Connect a fuel pressure gauge; pressure remains steady during the start-and-stall event. Connect a noid light to a fuel injector connector. During the start-and-stall, the noid light flashes briefly and stops, confirming the PCM cut the injector pulse command due to the B2960 fault.
    Tools: ['Fuel Pressure Gauge', 'Injector Noid Light'] (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Passlock State: Tamper / Fail (During crank attempt when fault occurs.)
• Passlock Data Voltage: <5.0V, but not matching learned value (During crank attempt; value is incorrect/unstable.)
• Battery Voltage: <11.5V (During crank; low voltage contributes to BCM misreading the sensor.)
• Vehicle Speed: 0 mph (Fault almost always occurs during engine start sequence.)

Related Codes

• P1631 — This powertrain code is a direct consequence of B2960. It means the PCM did not receive the correct 'start enable' password from the BCM. Diagnostically, P1631 is the result, while B2960 is the cause.
• B2958 — Indicates a specific electrical fault (a short to voltage) in the same circuit. B2958 often appears with B2960 when wiring or BCM connection issues are present.
• B3033 — Security System Tamper. Sets alongside B2960, especially in Saturn Ions, indicating the BCM detects an inconsistent signal from the ignition switch interpreted as tampering.
• U1000 — A generic Class 2 Data Link Malfunction code. Appears with B2960 if the security fault causes communication problems between the BCM and other modules.

Climate & Environmental Factors

• Cold Weather: Low temperatures cause plastic and metal components in the ignition lock cylinder to contract at different rates. This creates micro-gaps in electrical connections or alters the Passlock sensor magnet's alignment, pushing the resistance reading out of the BCM's expected range.
• High Humidity / Moisture: Moisture leads to corrosion on the pins of the Passlock sensor connector or the BCM connectors. Corrosion increases circuit resistance, which the BCM interprets as an invalid signal.

How to Talk to a Mechanic About This Code

Say this: "My GM vehicle has an intermittent no-start with a flashing security light, and I suspect a Passlock issue with code B2960. I'd like to book a diagnostic appointment. Please start by checking the Passlock sensor wiring, the ignition cylinder, and the BCM connections before recommending a BCM replacement."

This signals to the shop that you are informed about common failure points. It directs them to diagnose the most likely causes first (wiring, sensor) rather than immediately quoting a price for the most expensive part (the BCM).

Avoid saying:

• 'My car won't start.' (Too vague)
• 'The security light is on, I think it's the computer.' (Don't jump to the most expensive conclusion)
• 'Just replace the BCM.' (Never tell a shop what to replace without a proper diagnosis)

Questions to ask before authorizing the repair:

• Did you observe the Passlock voltage on a scan tool? Was it fluctuating or just incorrect?
• Have you inspected the wiring harness in the steering column for chafing or breaks?
• For Impalas/Monte Carlos: Did you check the terminal connections at the BCM as per TSB #04-08-47-003?
• If you are recommending a new ignition cylinder, does your quote include the mandatory 30-minute relearn procedure?
• What is the warranty on the parts and labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: A safe but expensive option. They are familiar with the issue but rarely opt for the most cost-effective repair path.
  Best for: Vehicles still under any form of warranty, Complex cases where multiple modules have failed and require programming with proprietary software.
  Downsides: Highest labor rates., Are often quick to replace the entire BCM or ignition lock cylinder assembly rather than diagnosing a simpler wiring fault. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit. A reputable independent shop servicing domestic vehicles knows the common shortcuts and TSBs, offering a good balance of expertise and value.
  Best for: Out-of-warranty GM vehicles., Shops with good reviews that mention experience with electrical or GM-specific issues.
  Downsides: Quality and experience varies greatly. Ensure the shop has technicians comfortable with electrical diagnostics. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. This is an electrical diagnostic issue. Chain shops are highly likely to misdiagnose it or recommend unnecessary, expensive repairs.
  Best for: Nothing related to this code. Their business model is not set up for in-depth electrical diagnostics.
  Downsides: Technicians are pressured to replace parts quickly rather than diagnose complex issues., Unlikely to have specific knowledge of GM Passlock TSBs or common wiring failure points. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost for the B2960 fault exceeds 40-50% of your car's private-party value, pause and consider your options. Stop DIY repairs if you lack a multimeter or are uncomfortable splicing wires.

• Car worth $2500, fix is $1100: Walk away. A $1100 BCM replacement on a $2500 car is not economical. Consider selling as a 'mechanic's special' or scrapping.
• Car worth $6000, fix is $550: Fix it. A $550 repair to replace the ignition lock cylinder is well below the threshold and makes the vehicle reliable again.
• Car worth $3500, fix is $150: Fix it. If the issue is wiring or a DIY bypass module, the cost is low enough to justify on almost any running vehicle.

What Scan Tool You Need for This Code

Minimum: A scanner that reads GM-specific Body Control Module (BCM) codes and views BCM live data. A basic engine code reader will NOT work.

A standard $20-50 reader only pulls engine (P) codes. B2960 is a body (B) code stored in the BCM. You must see BCM data like 'Passlock Data Voltage' to determine if the sensor, wiring, or BCM is the problem.

Budget: Xtool A30/A30M or Kingbolen Ediag Elite (~$90) — These Bluetooth dongles connect to a smartphone app and provide full system diagnostics, including the ability to read BCM codes and view live data streams.

Mid-range: Launch CRP129E or Foxwell NT series (~$250) — These dedicated handheld scanners offer full system access (BCM, etc.) and provide a more stable, all-in-one solution than Bluetooth dongles.

Professional: Autel MaxiCOM MK808 / MK906BT (~$450-1200) — Provides full bidirectional control, allowing you to command modules and run specific tests. This level of tool is what professional shops use to quickly diagnose complex electrical issues.

Rent vs buy: Auto parts stores offer free code reading, but their basic scanners typically cannot read BCM codes. Check if their loaner tool program includes a model that accesses GM BCM data.

How to Clear the Code After You Fix It

1. Reconnect battery
2. Use OBD-II scan tool to clear codes
3. Perform the 30-minute security relearn procedure if Passlock sensor or BCM was replaced.
4. Start the vehicle to confirm the fix and that the security light goes out

Drive cycle (~30 minutes): After repair, a full drive cycle sets emissions readiness monitors. Cold start, idle for 2-3 minutes. Drive in stop-and-go traffic for 5-10 minutes. Drive at steady highway speed (55-60 mph) for 15-20 minutes. Allow the vehicle to cool down completely.

Readiness monitors affected: Catalyst monitor, Evaporative System monitor, O2 sensor monitor

Before emissions retest: drive at least 50 miles to fully set monitors.

Watch out for:

• Forgetting to perform the mandatory 30-minute relearn procedure after replacing the ignition lock cylinder or BCM guarantees the vehicle does not start.
• Simply clearing the code with a scanner without fixing the root cause results in the code returning immediately on the next start attempt.
• Assuming a battery disconnect clears the fault; the BCM retains the learned Passlock value.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An illuminated 'SECURITY' light causes a visual inspection failure. The fault prevents the completion of a drive cycle, leaving readiness monitors incomplete.
• New York: Any malfunction indicator light related to the vehicle's operating systems, including the security light, is grounds for failure during the annual safety and emissions inspection.
• Texas: In the 17 counties requiring emissions testing, an illuminated warning light on the dashboard is grounds for an automatic failure.

Most Commonly Affected Vehicles

• Chevrolet Silverado / S-10 / Blazer (1998-2007) — Extremely common due to the Passlock II system. TSB #01-08-56-001A addresses wiring and connector issues on S/T platform trucks.
• GMC Sierra / Sonoma / Jimmy (1998-2007) — Mechanically identical to Chevrolet counterparts, sharing the same Passlock II system and high failure rates.
• Pontiac Grand Am / Sunfire (1999-2005) — Utilizes a version of the Passlock system highly prone to lock cylinder sensor failure.
• Chevrolet Impala / Monte Carlo (2000-2005) — GM TSB #04-08-47-003 points directly to poor terminal connections at the BCM connectors as a primary cause, often leading to needless BCM replacement.
• Chevrolet Malibu / Classic (1997-2005) — The Passlock system in these vehicles is a frequent source of no-start conditions and B2960 codes.
• Oldsmobile Alero / Bravada (1998-2004) — The Alero shares its platform with the Grand Am, while the Bravada relates to the Blazer. Both use the problematic Passlock system.
• Saturn Ion / L-Series (2003-2007) — TSB #06-08-47-003 for the 2006-2007 Ion recommends replacing the entire ignition switch due to inconsistent internal contacts setting B2960.
• Chevrolet Express / GMC Savana (2001-2007) — These work vans utilize the Passlock system and are highly susceptible to the start-and-stall condition.

Manufacturer-Specific Notes

• General Motors (All affected brands): This code is almost exclusively found on GM vehicles with Passlock I and Passlock II systems, which use a magnet in the ignition cylinder housing rather than a chip in the key.
• General Motors (W-Body Platform): On 2000-2005 Impalas and Monte Carlos, TSB #04-08-47-003 highlights poor terminal tension at the BCM connectors. Technicians must clean and tighten BCM connectors before replacing the module.
• Saturn: For the 2006-2007 Saturn Ion, TSB #06-08-47-003 points to the ignition switch itself as the primary culprit for B2960, rather than the lock cylinder housing.
• General Motors (Warranty/Recall): There are no active recalls for the Passlock sensor failure causing B2960. The major GM ignition switch recall (14V047) addressed a separate mechanical issue, making B2960 repairs customer-pay.
• Non-GM Brands: Code B2960 is not used by non-GM manufacturers. A B2960 code on a Ford, Toyota, or Honda indicates a scanner misinterpretation.

Real Owner Stories

2002 Chevy Impala with 150K miles starts and stalls.

Owner experienced intermittent start-and-stall with a flashing security light. A local shop quoted $700 to replace the BCM but couldn't guarantee a fix.

What they tried:

1. The owner found TSB #04-08-47-003 online, mentioning needlessly replaced BCMs due to poor connector contact.
2. Owner removed the driver-side dash panels, disconnected the BCM connectors (C1 and C2), cleaned the pins, and re-seated them firmly.

Outcome: The start-and-stall issue resolved completely. The problem was a poor connection at the BCM, not a faulty BCM itself. The fix cost $0 in parts.

Lesson: On 2000-2005 Impalas and Monte Carlos, always check and clean the BCM connectors per TSB #04-08-47-003 before spending hundreds on a new BCM.

1999 Chevy S-10 with intermittent no-start.

The truck intermittently started and immediately died, with the security light flashing. The owner needed a reliable, permanent fix without a high repair bill.

What they tried:

1. Owner located the three-wire harness from the ignition lock cylinder.
2. Following a DIY guide, they cut the yellow and orange/black wires.
3. They stripped and spliced the two cut ends leading towards the BCM together, bypassing the sensor entirely.

Outcome: After splicing the wires, the owner performed the 30-minute relearn procedure. The truck started reliably afterward, though the security light remained on constantly.

Lesson: A resistor-less bypass (splicing the two wires together) is a viable, near-zero-cost method to permanently fix the no-start issue if you accept the security light remaining on.

2004 Pontiac Grand Am won't start after a cold night.

The car cranked but would not start, with the security light flashing. The issue appeared suddenly after a temperature drop.

What they tried:

1. First attempt was the 10-minute trick. The car started once but failed again the next day.
2. Owner replaced the ignition lock cylinder with a new Dorman 924-713 unit.
3. After installation, the car still wouldn't start. The owner then performed the full 30-minute, 3-cycle relearn procedure.

Outcome: After the mandatory 30-minute relearn procedure was completed, the BCM learned the new lock cylinder's resistance value, and the car started normally.

Lesson: Replacing the Passlock sensor is a common fix, but the repair is incomplete and fails until the 30-minute security relearn procedure is performed.

How to Prevent This Code From Triggering

• Pause briefly in the 'ON' position before cranking (Every time you start the car) — Turning the key directly to 'Crank' causes voltage fluctuations. A 1-2 second pause allows the BCM to get a clean reading from the Passlock sensor before the starter engages.
• Apply dielectric grease to BCM and ignition connectors (Once, or whenever dash is accessed) — Dielectric grease blocks moisture and prevents corrosion on connector pins. Sealing these critical connections prevents future resistance-based faults.
• Minimize stress on the steering column harness (Daily habit) — Avoid heavy keychains and move the tilt column gently. This minimizes mechanical stress on the delicate Passlock sensor wires that chafe and break over time.
• Ensure battery terminals are clean and tight (Every oil change) — Poor connections at the battery cause intermittent voltage drops during cranking. A clean connection ensures the BCM receives stable voltage.

Frequently Asked Questions

Can I fix B2960 myself?

Yes. You can perform the 30-minute security relearn procedure for free. A permanent DIY fix involves installing a $50 Passlock bypass module to provide the BCM with a constant correct voltage.

What is the 10-minute trick for a GM security light?

Turn the key to 'ON' and wait exactly 10 minutes until the flashing security light goes solid. Turn the key off, wait 20 seconds, and start the car. This temporarily bypasses the fault but does not fix the root cause.

Will a new battery fix code B2960?

No. B2960 stems from an incorrect security sensor signal, not a general power failure. However, a severely weak battery causes voltage drops during cranking that exacerbate sensor misreads.

What is a Passlock bypass module and is it safe?

It is an electronic device wired into the security circuit that feeds the BCM a constant, correct voltage signal. This permanently fixes the B2960 code but disables the ignition cylinder's anti-theft feature.

Why did my car start and then die?

The Passlock system allows the engine to fire briefly while validating the key signal. Upon detecting the B2960 fault, the BCM instantly commands the PCM to cut fuel delivery, stalling the engine.

How do I tell a B2960 problem from a bad fuel pump?

Observe the 'SECURITY' light on the dashboard. If the car starts and dies while the security light flashes, the Passlock system is the culprit. If the security light behaves normally, investigate the fuel pump.

I replaced the ignition cylinder and the problem is still there. What now?

You must perform the mandatory 30-minute security relearn procedure so the BCM learns the new sensor's resistance value. If completed and the code persists, the fault lies in the wiring or BCM connectors.

What is the 'BCM terminal tightening' TSB for Impalas?

GM TSB #04-08-47-003 notes that loose terminals in the BCM connectors cause B2960 on 2000-2005 Impalas and Monte Carlos. Disconnect, clean, and tighten the BCM connections before replacing any expensive modules.

Key Takeaways

• Code B2960 is a General Motors-specific fault indicating the Body Control Module (BCM) received an incorrect voltage signal from the Passlock anti-theft sensor.
• The defining symptom is an engine that starts and immediately stalls within 1 to 3 seconds, accompanied by a flashing 'SECURITY' dashboard light.
• Before replacing parts, perform the free 30-minute security relearn procedure (three 10-minute key-on cycles) to rule out temporary system glitches.
• The most common permanent fix is replacing the worn ignition lock cylinder housing (costing $250 to $550) or installing an aftermarket resistor bypass module for under $50.