Principles of Operation

WARNING: This page is about a different car, the 2012 Ford Mustang. 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:

Correctly coded ignition key, from the Passive Anti-Theft System (PATS)
Clutch pedal applied, from the Clutch Pedal Position (CPP) switch, vehicles with manual transmission
Transmission in PARK or NEUTRAL, from the digital Transmission Range (TR) sensor, vehicles with automatic transmission
Starter motor request, ignition switch in the START position

When the ignition switch is placed in the START position, 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.

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

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