The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes value based on temperature) mounted in the intake manifold.

The low temperature produces a high resistance (100,000 ohms at -40°C/-40°F) while a high temperature causes a low resistance (70 ohms at 130°C/266°F).

The control module supplies a 5 volt signal to the sensor through a resistor in the control module and measures the voltage. The voltage will be high when the intake air is cold, and low when the air is hot. By measuring the voltage, the control module knows the intake air temperature.

The IAT signal is used by the control module in order to control the fuel.

The optical sensor sends what is called a High Resolution Signal and a Pump Cam signal to the PCM. There is a harness filter inline to the Optical/Fuel temperature sensor which is used in order to filter the shared 5 volt reference signal.

The APP module contains three potentiometers (a device for measuring an unknown voltage or a potential difference by comparison to a standard voltage). Each of the APP sensors send a varying voltage to the PCM. By monitoring the output voltage from the Accelerator Pedal Position (APP) module, the PCM can determine the fuel delivery based on the accelerator pedal position (driver demand).

The high resolution signal is an optical device which generates 64 equally spaced pulses per cylinder combustion stroke from the slotted disc mounted on the injection pump timing cam ring. The pulses are counted by the PCM and are used in order to measure the angular pump displacement. The fuel is metered by using the angular indication. The timing is measured by counting the angular pulses between the pump cam signal and the crankshaft position sensor signal.

The Injection Pump Cam signal is an optical device which generates one pulse per cylinder combustion stroke from a slotted disc mounted on the injection pump timing cam ring. The pulse is used to located the start of injection event for each cylinder (i.e. timing) with the respect to the crankshaft position sensor. The number one cylinder is identified with a wider pulse (larger slot in disc). The PCM uses this information in order to adjust the idle fuel, the timing and the trigger real time events. The Injection Pump Cam Signal is used in the diagnostics of the crankshaft position sensor and the high resolution circuit.

The Fuel Temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the injection pump.

The fuel temperature sensor is part of the optical/fuel temperature sensor. The resulting voltage is monitored by the PCM which uses this signal to minimize fueling error due to injection pump efficiency changes due to very hot fuel.

The crankshaft position sensor is a hall effect device which generates one pulse per cylinder combustion stroke from a four tooth reluctor wheel which is attached to the engine crankshaft. The pulse is used in order to locate the cylinder reference event (top dead center) for each cylinder. The PCM uses this information in order to adjust the timing, the trigger real time events and is used in the injection pump cam signal diagnostic.

The boost sensor measures the changes in the intake manifold pressure. The boost sensor converts the engine load and the speed changes, then converts the change in readings to the voltage output.

The PCM sends a 5 volt reference signal to the boost sensor. As the manifold pressure changes, the electrical resistance of the boost sensor also changes. By monitoring the sensor output voltage, the PCM detects the boost pressure. A high pressure (high voltage) requires more fuel. A lower pressure (low voltage) requires less fuel. The control module uses the boost pressure signal in order to control the fuel delivery.

The Boost sensor is also used for the BARO readings only on the vehicles that are not equipped with an EGR. This sensor reads the barometric pressure (BARO) under certain conditions, which allows the PCM to automatically adjust for different altitudes.

The VSS is attached to the output shaft housing. This device contains a permanent magnet surrounded by a coil of wire producing a magnetic field which is interrupted by rotor teeth pressed on an output shaft. As the rotor interrupts the magnetic field, an AC voltage is generated in the circuit.

The VSS buffer module is an electronic device. The VSS buffer module process inputs from the vehicle speed sensor and outputs various signals. The VSS buffer module outputs a 4000 pulse per mile signal. This signal is used by the PCM in order to determine the vehicle speed. The PCM uses the vehicle speed signal input for cruise control and fuel cutoff. The VSS buffer module is matched to the vehicle based on the transmission, the final drive ratio and the tire size. The VSS buffer module is located behind the instrument panel.

The fuel injector driver receives an inject command signal from the PCM and provides a current regulated output to the fuel solenoid that controls injection. The fuel injector driver also returns a fuel solenoid closure time signal back to the PCM in order to inform the fuel solenoid as to when the fuel solenoid has actually seated.

The TCC normally closed brake switch supplies a B+ signal into the PCM. The signal voltage is interrupted when the brakes are applied.

The cruise control normally open brake switch supplies a B+ signal to the PCM when the brake is applied. These signals are used by the PCM in order to control the transmission and the cruise control functions. The brake switches are part of the stoplamp switch.

The glow plug system is used in order to assist in providing the heat that is required in order to begin the combustion during the engine starting at the cold ambient temperatures.

The glow plug relay the switches power to the glow plugs and is commanded ON and OFF by the PCM. The glow plugs are heated before and during the cranking, as well as during the initial engine operation. The PCM monitors the glow plug relay output voltage which indicates if the relay is following the PCM commands.

The cruise control switches are part of the multifunction turn signal lever. These switches enable the driver to control the cruise ON/OFF, the set/coast, and the resume/accel signals. These signals are inputs to the fuel control portion of the PCM and allow the PCM to maintain a desired vehicle speed under normal driving conditions.

This signal indicates that the A/C compressor clutch is engaged. The PCM uses this signal in order to adjust the idle speed.