Chevrolet ECU IMMO Off
GM and Chevrolet vehicles use cluster-based anti-theft (Passlock I / Passlock II / PassKey / VATS) rather than ECU-level immobilizer modules common on European brands. There is generally no separate “ECU IMMO Off” service on GM vehicles — the anti-theft fault is almost always resolved by addressing the cluster, BCM, or Passlock chain.
What to do instead
- If you have a “Service Theft Deterrent System” message or no-start with security light flashing, see our Chevrolet Immobilizer / Passlock / VATS / PassKey Services hub.
- If your BCM has failed or been swapped, see our Chevrolet BCM / VBCM / Fuse Box Services hub.
- If you only need VIN written to a donor ECM, see our Chevrolet ECU VIN Programming hub.