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.
Electronic Engine Controls
The electronic engine controls consist of the following:
- Powertrain control module (PCM)
- Throttle position (TP) sensor
- Cylinder head temperature (CHT) sensor
- Camshaft synchronizer - 4.2L
- Camshaft position (CMP) sensor
- Crankshaft position (CKP) sensor
- Mass air flow (MAF) sensor
- Heated oxygen sensor (HO2S)
- Catalyst monitor sensor
- Knock sensor (KS)
- Vehicle speed sensor (VSS)
The PCM needs the following inputs to calibrate the engine correctly:
- CMP sensor
- Engine rpm
- Cylinder head temperature
- Amount of engine detonation
- Crankshaft position
- Air temperature
- Throttle position
- Cylinder head temperature
- Mass airflow
- Exhaust oxygen content
The TP sensor:
- sends the PCM a signal indicating the throttle plate angle.
- is the main input to the PCM from the driver.
- is incorporated into the electronic throttle body on 4.2L and 4.6L engines.
The CHT sensor:
- is mounted to the wall of the cylinder head and is not connected to any coolant passages.
- sends the PCM a signal indicating cylinder head temperature.
- As the cylinder head temperature rises above normal operating temperature, the PCM will turn on the high speed cooling fan. If the temperature continues to rise, the PCM will selectively and alternately disable fuel injectors. The cylinders that are not being fuel injected will act as air pumps to aid in engine cooling. The PCM will also turn on the check engine light and set a DTC. If the cylinder head temperature continues to rise, the check engine light will begin to flash and an additional DTC will be set. Finally, if the cylinder head temperature rises still more, the PCM disables all of the fuel injectors, turning the engine off.
The CMP sensor:
- sends the PCM a signal indicating camshaft position used for fuel synchronization.
The CKP sensor:
- sends the PCM a signal indicating crankshaft position.
- is essential for calculating spark timing.
The MAF sensor:
- sends the PCM a signal indicating mass airflow rate of air entering the engine.
- sends the PCM a signal indicating the temperature of the air entering the engine.
The HO2S:
- has the ability to create a voltage signal dependent on exhaust oxygen content.
- provides feedback information to the PCM used to calculate fuel delivery.
The 4.2L KS is located on the rear of the LH cylinder head. The 4.6L KS is located in the lifter valley. The 5.4L has a unique linear KS located in the lifter valley.
- The KS sends a signal to the PCM indicating engine detonation.
The VSS:
- is gear driven by the transmission.
- sends a signal to the PCM indicating vehicle speed. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION - 4R70E/4R75E article.
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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.