Ford Focus Service Manual: Electronic Engine Controls

Ford Focus Service Manual / Powertrain / Internal Combustion Powertrain Control / Engine Control / Electronic Engine Controls

The electronic engine controls consist of the following:

PCM
Cylinder Head Temperature (CHT) sensor
Camshaft Position (CMP) sensor
Crankshaft Position (CKP) sensor
Power Steering Pressure (PSP) switch
Mass Air Flow (MAF) sensor
Heated Oxygen Sensor (HO2S)
Catalyst Monitor Sensor (CMS)
Knock Sensor (KS)
Swirl control valve sensor

The PCM:

accepts input from various engine sensors to compute the fuel flow rate and spark timing 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 CHT sensor:

sends the PCM a signal indicating cylinder head 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 PSP switch:

is a normally closed switch that opens as pressure increases.
is used to send a signal to the PCM to adjust idle speed. This compensates for additional load on the engine from the power steering pump.

The MAF sensor:

uses a hot wire sensing element to measure the amount of air entering the engine.
uses a second hot wire to measure intake air temperature.
sends signals to the PCM. The PCM will then calculate the required fuel injector pulse width in order to provide the desired air/fuel ratio.

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 catalyst efficiency.

The KS :

sends a signal to the PCM indicating engine detonation, which retards the ignition timing as necessary.

The swirl control valve sensor:

monitors the position of the swirl control lever.

Engine Control

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Diagnostic Parameters Identification (PID) Chart

Using Output State Control and Accessing PIDs To confirm that the output state control value was sent by the scan tool and the PCM has accepted the output state control substitution, a correspondi ...

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