Your Vehicle: 2001 Ford Escort ZX2 L4-2.0L DOHC VIN 3
Vehicle » Powertrain Management » Computers and Control Systems » Description and Operation » System Components  
  System Components  

Powertrain Control Module (PCM)
The Powertrain Control Module (PCM) uses data it receives from various sensors, switches and relays to generate output signals to control relays, solenoids and other components. The PCM will compensate for changes in altitude.

Throttle Position (TP) Sensor
The Throttle Position (TP) sensor is a rotary potentiometer in which the PCM determines four operating modes from the TP sensor signal. These are:

  • closed throttle (idle or deceleration)
  • part throttle (cruise, moderate acceleration)
  • Wide Open Throttle (WOT) (maximum acceleration)
  • throttle angle rate

Mass Air Flow (MAF) Sensor
The Mass Air Flow (MAF) sensor measures the mass of the air flowing into the engine. The PCM uses the MAF sensor signal to calculate the fuel injector pulse width.

Intake Air Temperature (IAT) Sensor
The PCM uses the Intake Air Temperature (IAT) sensor signal to proportion the cold enrichment fuel flow and as a density corrector for air flow calculations. The IAT sensor is incorporated into the MAF sensor and repaired as an assembly with the MAF sensor.

Power Steering Pressure (PSP) Transducer
The Power Steering Pressure (PSP) transducer sends a signal to the PCM to increase idle speed for engine stability when power steering pump pressure increases above a set pressure value.

Idle Air Control (IAC) Valve
The Idle Air Control (IAC) valve is used to control engine idle speed. The amount of air allowed to bypass the throttle plate is determined by the PCM.

Engine Coolant Temperature (ECT) Sensor
The Engine Coolant Temperature (ECT) sensor signal is used by the PCM to modify ignition timing and the air-to-fuel ratio.

Heated Oxygen Sensors (HO2S)
The upstream Heated Oxygen Sensor (HO2S) is mounted in the exhaust manifold and senses the oxygen concentration in the exhaust gas. It sends this information to the PCM, which uses the information to determine fuel injection amounts. The sensing element is made of zirconia ceramic with a platinum coating.

The downstream HO2S is mounted on the muffler inlet pipe just below the Three Way Catalytic Converter (TWC) . The downstream HO2S monitors the TWC and transmits the information to the PCM.

Camshaft Position (CMP) Sensor
The Camshaft Position (CMP) sensor provides a signal to the PCM when the number one piston is on the compression stroke.

Crankshaft Position (CKP) Sensor
The Crankshaft Position (CKP) sensor provides crankshaft position and rpm information to the PCM.The CKP sensor is:

  • a variable reluctance type sensor.
  • activated by a 36 minus one tooth wheel.

Knock Sensor (KS)
The Knock Sensor (KS) is used to detect engine detonation (spark knock). As a result, a voltage signal is sent to the PCM which retards the ignition timing as necessary.

Fuel Pressure Sensor
The fuel pressure sensor senses the pressure difference between the fuel injection supply manifold and the intake manifold, and provides the PCM with the current fuel injection supply manifold pressure. The return fuel line to the fuel tank has been deleted in this type of fuel system.

The PCM uses this information to vary the duty cycle output to the Fuel Pump Driver Module (FPDM) which controls the speed of the fuel pump. The speed of the fuel pump sustains fuel injection supply manifold pressure which preserves fuel in its liquid state.

The dynamic range of the fuel injector's increase is due to the higher pressure, which allows the injector pulse width to decrease.

Variable Camshaft Timing (VCT)
The Variable Camshaft Timing (VCT) unit is connected to the exhaust camshaft, and the rotation of the exhaust camshaft takes place in the VCT unit. The unit is oil-filled to move the pistons inside the VCT unit. The oil and piston movement inside the unit can retard the exhaust camshaft without affecting the intake camshaft.

The VCT unit variable adjustment allows every piston position between maximum advance and maximum retardation.

Oil Control Solenoid
The oil control solenoid is part of the VCT unit.

Fuel Pump Driver Module (FPDM)
The Fuel Pump Driver Module (FPDM) regulates the voltage to the fuel pump to achieve the correct fuel pressure.


  • receives a duty cycle signal from the PCM.
  • controls the fuel pump operation in relation to the duty cycle signal to compensate for varying loads.
  • sends diagnostic information to the PCM on the fuel pump monitor circuit.