Engine Immobilizer System: Prius

Engine immobilizer system may also be referred to as Hybrid Vehicle (HV) immobilizer system. Engine immobilizer system is a theft deterrent system that disables hybrid system and prevents engine from starting by not allowing fuel injector and ignition system operation unless ignition key identification code matches code stored in Hybrid Vehicle (HV) control Electronic Control Unit (ECU). Hybrid vehicle control ECU is referred to as HV ECU.

Engine immobilizer system consists of ignition key with transponder chip incorporated in top of ignition key, transponder key coil, transponder key ECU and HV ECU. When ignition is turned on, transponder key ECU checks if ignition key is registered and delivers the result to the HV ECU. When HV ECU confirms ignition key is registered, it transmits its own identification numbers to the transponder key ECU. The transponder ECU then calculates internally and delivers the calculated result back to the HV ECU. The HV ECU rechecks the calculated result against calculation stored in the HV ECU. If calculations are the same, the HV ECU allows hybrid system operation and allows the engine to start. If calculations are not the same, the HV ECU will not allow hybrid system operation and the engine to start. For additional information on system operation and testing, see appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.