OBD2 code B0420: Anti-theft system/alarm
Anti-theft system fault.
Detected Root Component
Body Component
Observed Symptoms
- Faulty central locking
- Dashboard errors
- Unable to start
Possible Causes
- Faulty BCM module
- Defective sensor
- Incorrect module configuration
- Damaged wiring
Tools Required
Interactive Diagnostic
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Diagnostic Result
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Parts likely to be the cause (Boîtier fusibles / BSI)
Boîtier fusibles / BSI
Photo d'illustration : Boîtier fusibles / BSI
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Frequently asked questions about code B0420
What does code B0420 mean? ▾
OBD2 code B0420: Anti-theft system/alarm. Anti-theft system fault.
What are the symptoms of code B0420? ▾
Code B0420 may cause: Faulty central locking, Dashboard errors, Unable to start. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code B0420? ▾
The most common causes of code B0420 are: Faulty BCM module, Defective sensor, Incorrect module configuration, Damaged wiring. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code B0420? ▾
Code B0420 has moderate severity (Warning). Short-term driving remains possible, but a prompt check is recommended to prevent worsening.
How do I fix code B0420? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Faulty BCM module, Defective sensor, Incorrect module configuration, Damaged wiring. Difficulty: Easy · Estimated time: 30-60min.