Electronic Engine Controls
WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 Ford Escape. 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)
- Cylinder head temperature (CHT) sensor
- Throttle position (TP) sensor
- Idle air control (IAC) valve
- Camshaft position (CMP) sensor
- Crankshaft position (CKP) sensor
- Mass air flow (MAF) sensor
- Heated oxygen sensor (HO2S)
- Catalyst monitor sensor
- Knock sensor (KS)
- Manifold absolute pressure (MAP) sensor
The PCM carries out the following functions:
- accepts input from various engine sensors to compute the fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire engine operational range.
- outputs a command to the fuel injectors to meter the appropriate quantity of fuel.
The CHT sensor:
- sends the PCM a signal indicating cylinder head temperature.
- resistance decreases as coolant temperature increases.
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 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:
- uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool.
The HO2S:
- creates a voltage signal dependent on exhaust oxygen content.
- provides feedback information to the PCM used to calculate fuel delivery.
The catalyst monitor sensor:
- monitors oxygen content after it flows through the catalytic converter.
- provides a voltage to the PCM used to calculate catalytic converter integrity.
The KS:
- is used to detect engine detonation.
- sends a voltage signal to the PCM.
- is able to provide a signal which retards the ignition timing, as necessary.
The MAP sensor:
- measures manifold vacuum and converts it to an electrical signal. This provides the PCM information on engine load.