B2498

Code

Generic B — Body

Immobilizer — Key Code Not Recognized

Brand: Generic

Type: B — Body

Views: UK: 15 EN: 33 RU: 18

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Unprogrammed or erased key/transponder
Damaged or faulty key transponder or key electronics
Faulty immobilizer control module or receiver (antenna coil)
Open, shorted or corroded wiring/connectors between key reader and immobilizer module
Low vehicle battery or weak key fob battery affecting transponder communication
PCM/ECM not accepting immobilizer authorization due to software or communication fault

Symptoms

Engine will not start or cranks but will not run
Security/immobilizer warning lamp illuminated or flashing
No crank in some vehicles (starter disabled) depending on system
Key not detected message on dash or instrument cluster
Intermittent starting—sometimes starts with spare key
Remote lock/unlock may still work (depends on system) or keyless start nonfunctional

What to check

Use a scan tool to read B2498 and any related codes from immobilizer, BCM and powertrain modules
Verify vehicle and key battery voltages (vehicle battery >= 12.4 V; replace weak key fob battery)
Try a known-good or spare programmed key to see if the vehicle recognizes it
Observe immobilizer/security lamp behavior during key insertion and crank
Check antenna coil/reader around ignition or push-button area for physical damage and secure mounting
Inspect wiring and connectors between antenna, immobilizer module and PCM for corrosion, loose pins, or damage

Signal parameters

Transponder ID code read by immobilizer (valid/invalid or null)
Antenna coil waveform or voltage pulses when key presented
Immobilizer module supply voltage and ground status
Key-present flag and key ID messages on CAN bus
Authorization/OK message from immobilizer to PCM (allowed/denied)
Security lamp status (on/off/blink rate) as reported by module

Diagnostic algorithm

Confirm symptom and gather history: number of keys, recent battery changes, aftermarket installs, or module replacements.
Scan all modules (BCM, immobilizer, PCM) and record stored and pending DTCs and freeze frame data.
Verify vehicle and key battery condition. Replace weak batteries and retry key recognition.
Attempt start with a known-good/programmed spare key. If spare works, suspect primary key failure—test or replace key.
Observe immobilizer/security lamp while inserting key/pressing start; note normal or abnormal lamp patterns and correlate with service manual.
Check antenna/reader: inspect for damage, test continuity, measure coil resistance per manufacturer specs, and verify connector terminals.
Inspect wiring and grounds between antenna, immobilizer module and PCM. Repair any damaged wiring or poor grounds.
Use diagnostic tool to read live data: transponder ID, key-present status, and authorization messages. If transponder ID is blank or invalid, transponder/key likely defective or unprogrammed.
If key is unprogrammed or corrupted, reprogram key using manufacturer-approved tool and procedures. Confirm immobilizer and PCM learn procedures are completed.
If the immobilizer module or antenna is faulty and cannot communicate properly with valid keys, follow module replacement and programming procedures. Replace only after verifying coding/programming requirements.
After repairs, clear codes and retest multiple start cycles and with each key. Monitor for reappearance of B2498 or related codes before concluding repair.