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:
- PCM.
- throttle position (TP) sensor.
- idle air control (IAC) valve.
- engine coolant temperature (ECT) sensor (3.0L and 4.0L).
- camshaft position (CMP) sensor.
- crankshaft position (CKP) sensor.
- mass air flow (MAF) sensor.
- manifold absolute pressure (MAP) sensor (2.3L).
- intake air temperature (IAT) sensor.
- heated oxygen sensor (HO2S).
- catalyst monitor sensor.
- wheel speed sensor.
- cylinder head temperature (CHT) sensor (2.3L).
The PCM:
- accepts input from various engine sensors to compute the fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire engine operating range.
- outputs a command to the fuel injectors to meter the appropriate quantity of fuel.
The TP sensor:
- sends the PCM a signal indicating the throttle plate angle.
- is the main input to the PCM from the driver.
The IAC valve:
- controls bypass air around the throttle plate at low speeds.
- is controlled by the PCM.
The ECT sensor (3.0L and 4.0L):
- sends the PCM a signal indicating engine coolant temperature.
- resistance decreases as coolant temperature increases.
The CHT sensor (2.3L):
- sends the PCM a signal indicating cylinder head temperature.
The CMP sensor:
- provides camshaft position information which is used by the PCM for fuel synchronization.
The CKP sensor:
- sends the PCM a signal indicating crankshaft position.
- is essential for calculating spark timing.
The MAF sensor:
- uses a hot wire sensing element to measure the amount of air entering the engine.
- sends the PCM a signal to determine the intake air mass. The PCM will then calculate the required fuel injector pulse width in order to provide the desired air/fuel ratio.
The MAP sensor:
- measures manifold vacuum and converts it to an electrical signal. This provides the PCM information on engine load.
The IAT sensor (3.0L and 4.0L):
- sends the PCM a signal indicating the temperature of the air entering the engine.
- resistance decreases as temperature increases.
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 catalyst monitor sensor:
- 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 wheel speed sensor:
- sends a signal to the PCM indicating wheel speed.
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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.