Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD2012EXPEDITION 2WD V8-5.4LREPAIR AND DIAGNOSISSTARTING AND CHARGINGSTARTING SYSTEMTESTING AND INSPECTIONINITIAL INSPECTION AND DIAGNOSTIC OVERVIEWPRINCIPLES OF OPERATION
2012 Ford Expedition 2WD V8-5.4L
Principles Of Operation
2012 Ford Expedition 2WD V8-5.4LSECTION Principles Of Operation
Starting System
Principles of Operation
Starting System
The starting system is electronically controlled by the PCM. The PCM receives the following inputs:
- Transmission in PARK or NEUTRAL, from the Transmission Range (TR) sensor
- Correctly coded Passive Anti-Theft System (PATS) ignition key
- Ignition switch input, when ignition switch is in the START position
When the ignition switch is turned to the START position, the PCM receives battery voltage on the starter switch input circuit. If the PCM receives other input signals indicating that it is OK to start the engine (TR (Transmission Range) sensor input, PATS (Passive Anti-Theft System) key input), it provides the starter relay coil with both voltage and a ground. The starter relay contacts close, supplying voltage to the starter solenoid, which activates the starter motor. Once the starter motor begins to crank, the ignition switch may be released to the RUN position. The starter motor will continue to crank until either the engine starts, a PCM-controlled crank time has been exceeded or the ignition switch is turned to the OFF position.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.