Magazine for the auto service professional
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Circle 111 on Reader Service Card 24 | September/October 2014 the vehicle. Most vehicles outftted with a smart key system will include a mechanical backup key. After exiting the vehicle, doors are locked by either pressing a button on the door handle, touching the door han- dle's capacitive area, or in some models, by simply walking away from the vehicle (as the smart key recognizes a specifc distance away from the vehicle, the doors lock). An engine immobilizer system uses a tran- sponder chip in the ignition key (or remote fob). The system features a transponder key ECU assembly that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthor- ized key, the system's ECU sends a signal to the primary ECM to prohibit fuel delivery and ignition, effectively disabling the engine. Citing Toyota systems as an example, system components include a transpon- der key coil/amplifer, an unlock warning switch assembly, a dedicated system ECU and a security indicator. The transponder key coil receives a key code when the key is inserted into the ignition key cylinder. The ID code is then amplifed and outputs the code to the tran- sponder key ECU. The unlock warning switch assembly detects if the key is in the ignition cylinder and out- puts results to the transponder key ECU. The primary ECM receives ID verifcation results from the transponder key ECU. The ECM also verifes the immobilizer system's ECU, allowing fuel and spark delivery. When the transponder key ECU assembly detects that the key unlock warning switch The Tech Bench With the smart key fob inside the vehicle, push button engine starting is enabled with- out the need for a mechanical key.