OBD Guide
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B1A6C

Secret Key Mismatch

B1A6C is an OBD-II diagnostic trouble code meaning: Secret Key Mismatch. Common causes: the battery in the key body is low or faulty, oxidation of contacts on the key chip. Estimated repair cost: $11–278.

Severity
🚨 Critical
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$11–278 (est.)

Symptoms

  • The engine does not start when the ignition is turned on
  • The immobilizer indicator on the dashboard is on
  • Error message on the multimedia system display
  • Starting is only possible with a special spare key
  • Intermittent crashes when trying to start

Causes

  • The battery in the key body is low or faulty
  • Oxidation of contacts on the key chip
  • The immobilizer module is switched to the wrong mode or there is a memory failure
  • Non-original or copied key without synchronization
  • Damage to the reader antenna wiring harness near the ignition switch
  • RFID reader failure in ignition switch
  • Immobilizer module power supply problem
  • Trying to use a key from another car
  • Programming error when replacing electronic control module

How to Fix

  1. Diagnostics using an OBD-II scanner to confirm the B1A6C code
  2. Visual check of the condition of the keys (cleanliness of contacts, integrity of the microcircuit)
  3. Checking the batteries in the key body and replacing them if necessary
  4. Inspect the immobilizer system wiring harness under the steering column for damage.
  5. Checking the supply voltage on the immobilizer module (usually 12V)
  6. Switching to key programming mode according to the car manufacturer's instructions
  7. Deleting all current keys from memory and reprogramming the main key
  8. Checking whether the key chip ID matches the data in the controller
  9. If necessary, replace the immobilizer module with subsequent rewrite of its code
  10. Testing all keys for correct startup

Related codes

B1A60B1A61B1A62B1A65P0600P0606

FAQ

What does the B1A6C code mean?

B1A6C is an OBD-II diagnostic trouble code that indicates: Secret Key Mismatch

What causes a B1A6C error code?

The most common causes of B1A6C include: The battery in the key body is low or faulty; Oxidation of contacts on the key chip; The immobilizer module is switched to the wrong mode or there is a memory failure; Non-original or copied key without synchronization.

How do I fix a B1A6C diagnostic trouble code?

To fix B1A6C: Diagnostics using an OBD-II scanner to confirm the B1A6C code. Visual check of the condition of the keys (cleanliness of contacts, integrity of the microcircuit). Checking the batteries in the key body and replacing them if necessary. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1A6C?

Yes, but get it checked soon

How much does it cost to fix B1A6C?

The estimated repair cost for B1A6C is $11–278. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat