Principles of Operation: Notes

WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The starting system is electronically controlled by the PCM. The PCM receives the following inputs:

Transmission in PARK or NEUTRAL, from the digital Transmission Range (TR) sensor (located In the transmission)
Correctly coded ignition key, from the Passive Anti-Theft System (PATS), vehicles equipped with PATS
Starter motor request, ignition switch in the START position

When the ignition switch is placed in the START position, voltage is supplied to the Body Control Module (BCM) internal logic. A starter motor request signal is also sent to the PCM. If the PCM recognizes the correct input signals, it provides the starter relay coil with both voltage and ground. The starter relay contacts close, providing voltage to the starter solenoid, allowing the starter motor to activate. The starter motor continues to crank until the ignition key is released from the START position.

Vehicles equipped with an automatic transmission have a digital TR sensor. The digital TR sensor prevents operation of the starter motor unless the transmission is in NEUTRAL or PARK.

Manual transmission equipped vehicles have a CPP switch. The CPP switch prevents operation of the starter motor unless the clutch pedal is fully pressed.