Originally Posted by
TODD
The passkey module can block vehicle operation two ways:
1. When correct key resistance is detected, passkey module completes the circuit to the starter enable relay coil. This enables the ignition switch to energize the starter solenoid during starting. The circuit is interrupted when the passkey module detects a problem with the key resistance.
Power for the starter enable relay coil comes from fuse 1A. This fuse also supplies the SDM airbag module. If this fuse is pulled, car will not start. Removal of Fuse 1C instead will disable the airbags.
2. The passkey module generates a PWM square-wave signal when it detects correct resistance on the key. This signal is then fed into the power train control module to enable the fuel injectors. If this signal is absent at the PCM, no fuel is supplied. Since this feature would be very difficult to disconnect or bypass, the passkey system has to be kept in operation.
The passkey system will activate the security warning light if it is blocking vehicle operation.
The universal theft deterrent system (door/trunk/horn alarm system) can also activate the security light. Those alarms do not affect vehicle starting.