B2191 on Infiniti: How to Diagnose & Fix
Manufacturer-Specific Body Code (Nissan/Infiniti: Difference of Key / NATS ID Mismatch)
1 Infiniti model · 1 documented issue · 1 critical · $600-$1,800 repair
B2191 on Infiniti by model: symptoms, diagnosis and fix
Infiniti/Nissan vehicles using the electronic steering column lock system have a well-documented failure mode where the vehicle will not recognize the lock state, leaving the car unable to start even though the battery and key fob appear normal. The issue is widely discussed across Nissan/Infiniti owner communities and tied to the steering lock control unit used on related FM-platform vehicles. Owners typically report a sudden no-start with the steering wheel locked or the ignition staying in ACC/ON behavior without cranking.
Common Symptoms
- push-button start does nothing
- vehicle stuck in ACC or ON mode
- steering remains locked
- intelligent key warning
- intermittent no-start that becomes permanent
How to Fix
Confirm battery voltage and key fob operation first, then scan BCM/IPDM/steering lock modules for communication or lock-status faults. Repair usually involves replacing or bypassing the failed electronic steering lock assembly depending on model applicability and local repair practice, followed by key/immobilizer relearn if required. Because symptoms mimic a weak battery or bad brake switch, proper diagnosis is important before replacing parts.
Owner tips & cautions
- TipBefore condemning the steering lock, verify the 12V battery is fully charged and load-tested; low voltage can trigger misleading intelligent-key and lock errors.
- TipIf the vehicle intermittently fails to start, scan BCM and immobilizer modules immediately while the fault is active; stored history can disappear after battery disconnects.
Sources for this issue (2)
B2191 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 B2191 mean on a Infiniti?
B2191 stands for "Manufacturer-Specific Body Code (Nissan/Infiniti: Difference of Key / NATS ID Mismatch)." B2191 is a manufacturer-specific body code. On Nissan and Infiniti vehicles it generally means 'Difference of Key' — the body control module and the NATS Intelligent Key failed ID verification, so the key the system read does not match a registered key. As a security/anti-theft fault, the immobilizer may prevent the engine from starting or the steering lock from releasing. On other makes the meaning could differ, so confirm against the specific service data. On Infiniti it is documented across 1 model: QX50.
What are the most common causes of B2191?
The most common causes of B2191 are: Unregistered or incorrect key/transponder being used, Faulty Intelligent Key or transponder, Wiring fault between key slot/antenna and BCM, Failed key-slot or antenna amplifier, Body control module (BCM/NATS) fault, Interference or low key battery. The specific cause varies by vehicle.
How much does it cost to fix B2191 on a Infiniti?
Published repair estimates on Infiniti range from $600 to $1,800 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.
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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.