Ford Workshop Service and Repair Manuals

The engine management system consists of a powertrain control module and a number of sensors and actuators. The sensors supply the powertrain control module with input signals which relate to engine operating conditions and the actuators respond to output signals from the powertrain control module. These output signals are based on the evaluated input signals which are compared with calibrated data tables or maps before the output signal is generated.

Powertrain Control Module (PCM)

The engine management system utilizes a 104-pin powertrain control module (EEC V) which provides precise control of basic engine calibration parameters. The powertrain control module is protected by a steel security cover to maintain the integrity of the passive anti-theft system. The security cover is retained by two steel rivets.

Heated Oxygen Sensor (HO2S)

The heated oxygen sensor is a voltage generator which is installed ahead of the catalyst in the exhaust flow. When the air/fuel ratio is ideal (theoretically 14.7:1) or Lambda 1, a voltage signal of 450 mV is sent to the powertrain control module. When the mixture is lean, the voltage signal is reduced to 200 mV and the powertrain control module sets the air/fuel mixture towards rich. When the mixture is rich, the voltage signal is increased to 800 mV and the powertrain control module sets the air/fuel mixture to lean. This provides close control of exhaust emissions. To ensure the heated oxygen sensor quickly reaches it's operating temperature of 300°C, it is equipped with a heating element which operates when the ignition is switched on.

Camshaft Position (CMP) Sensor

The camshaft position sensor is an inductive pulse generator which scans a reference cam on the camshaft. The camshaft position sensor sends an alternating voltage signal to the powertrain control module from which the position of number one cylinder is calculated. The signal from the camshaft position sensor is required only during starting. When the engine is running, the profile ignition pick-up (PIP) signal is used to sequentially control the fuel injectors.

Crankshaft Position (CKP) Sensor

The crankshaft position sensor is an inductive pulse generator which scans 36-1 cast protrusions on the flywheel. Minus one means that one of the cast protrusions is missing and this gap is located at 90° before top dead centre. This gap is used by the powertrain control module as a reference for crankshaft position. The crankshaft position sensor sends an alternating voltage signal to the powertrain control module where it is converted and becomes the digital, profile ignition pick-up (PIP) signal.

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature sensor is a temperature dependent resistance which has a negative temperature coefficient i.e. it's temperature changes inversely with respect to temperature. The engine coolant temperature sensor is supplied with a reference voltage by the powertrain control module. When the engine coolant temperature changes, the resistance of the sensor changes thus changing the output voltage. The output voltage is assigned to a corresponding engine coolant temperature by the powertrain control module.

Mass Air Flow (MAF) Sensor

The mass air flow sensor measures the mass of air entering the intake system, the measurement being based on the constant temperature hot wire principle. Suspended in a bypass duct are a hot wire probe and an air temperature probe. The powertrain control module ensures that the hot wire probe is always 200°C hotter than the air temperature probe. The hot wire probe is cooled by the air flowing through the intake system and the powertrain control module varies the heating current to maintain the 200°C temperature difference. The change in heating current is measured as a voltage drop across a precision resistor and is assigned to a corresponding mass air flow calculation by the powertrain control module.

Throttle Position (TP) Sensor

The throttle position sensor is a rotary potentiometer which is secured to the throttle body and operated by the throttle plate shaft. The throttle position sensor is supplied with a reference voltage by the powertrain control module. When the throttle plate is opened, a sliding contact moves over a resistance track changing the output voltage. The output voltage is assigned to a corresponding throttle plate position by the powertrain control module.

Idle Air Control (IAC) Valve

The idle air control valve is an electronically controlled solenoid valve which allows a flow of air to bypass the throttle plate. Engine speed can, therefore, be maintained irrespective of engine load. The idle air control valve is controlled by grounding pulses from the powertrain control module, the length of which determines the position of the valve.

Intake Air Temperature (IAT) Sensor

The intake air temperature sensor is a temperature dependent resistor which has a negative temperature coefficient i.e. it's temperature changes inversely with respect to ambient temperature. The intake air temperature sensor is supplied with a reference voltage by the powertrain control module. When the intake air changes temperature, the resistance of the sensor changes thus changing the output voltage. The output voltage is assigned to a corresponding intake air temperature by the powertrain control module.

Power Steering Pressure (PSP) Switch

The power steering pressure switch monitors the hydraulic pressure within the power steering system. The switch is a normally open switch that closes as the hydraulic pressure increases. The powertrain control module uses the input from the switch to compensate for additional loads on the engine by adjusting the engine idle speed and preventing engine stall during parking maneuvers.