Electronic Engine Controls
WARNING: This page is about a different car, the 2004 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.
The electronic engine controls consist of the following:
- Powertrain control module (PCM).
- Throttle position (TP) sensor.
- Idle air control (IAC) valve.
- Engine coolant temperature (ECT) sensor.
- 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.
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:
- sends the PCM a signal indicating engine temperature.
- resistance decreases as coolant temperature increases.
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 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.