Electronic Engine Controls
The electronic engine controls consist of the following:
- PCM
- Throttle Position (TP) sensor
- Idle Air Control (IAC) valve
- Engine Coolant Temperature (ECT) sensor (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 (CMS)
- 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 (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 (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 CMS:
- 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.