Bxxxx · Body
B2103
Antenna Coupling Coil Circuit Failure
CriticalBody ECU
What it means
The immobilizer antenna ring around the ignition lock cylinder is not transmitting the RF challenge to the key transponder. Vehicle will not start.
Common causes
Listed in rough order of frequency. Verify with vehicle-specific service info before parts replacement.
- 01Failed immobilizer antenna ring
- 02Damaged or disconnected antenna harness
- 03Faulty immobilizer / smart-entry ECU
- 04Aftermarket alarm or remote-start install damaging factory wiring
Affected systems
ECUs and subsystems that report or are affected by this code.
Immobilizer ECUAnti-theft system
Get vehicle-specific diagnosis for B2103
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Ask the forums about B2103Critical-severity code
This code typically prevents the vehicle from starting, running normally, or operating safely. Diagnose carefully before clearing — clearing without fixing the root cause often masks deeper problems.