4A63
Critical4A63 — EWS: Immobilizer Tampering
Description
What the Code Means
4A63 is logged by the CAS module when the EWS (electronic immobilizer) system detects tampering: an attempt to bypass the immobilizer or use an unauthorized key. CAS stores the code as a security violation record. In normal operation, the handshake between the key, CAS, and DME confirms authenticity on every start; the CAS treats a signature mismatch as unauthorized access.
Symptoms
Symptoms
- Engine won't start
- Immobilizer warning light comes on
- The car doesn't recognize the key
Causes and fixes
Diagnosis and Repair
- Read the EWS status with ISTA and confirm which type of tampering was recorded.
- Check key synchronization with the CAS module.
- When installing a used CAS, replace the DME and all keys: mismatched modules won't accept each other's signatures.
- Program the new CAS module.
- Clear the codes and do a test start.
Possible secondary damage
Indirect Issues
- The immobilizer can permanently block engine start; recovery requires replacing the CAS and DME modules. Don't put off the fix: unlocking later without replacing components isn't possible.