Inputs

Coolant Temperature Sensor (CTS)
The coolant temperature sensor, which is located on the left hand side of the cylinder block below the exhaust manifold, provides engine temperature input to the Electronic Control Unit. The ECU will use the inputs from the CTS when coolant temperature are cold, to enrich the air/fuel mixture, control engine warm-up idle speed, increase ignition advance and inhibit the EGR system.

Manifold Air Temperature (MAT) Sensor
The manifold air temperature sensor, which is located in the intake manifold, provides an air temperature input to the ECU. The ECU in turn will compensate for air density changes during high temperature operation.

Manifold Absolute Pressure (MAP) Sensor
The manifold absolute pressure sensor is located on the firewall behind the engine. A hose from the intake manifold provides the input pressure for the sensor. The sensor will react to absolute pressure in the intake manifold and will provide an input voltage to the ECU. The signal from the MAP sensor supplies the ECU with mixture density information and ambient barometric pressure information.

Oxygen Sensor
The Exhaust Gas Oxygen Sensor is NOT a voltage generating device. This sensor detects exhaust oxygen content by acting as a variable resistor. The exhaust gas oxygen sensor provides the ECU with a feedback signal. By measuring the amount of oxygen in the exhaust gases, the oxygen sensor tells the ECU how well its output signals are properly controlling the air/fuel ratio. Based on this feedback, the ECU can adjust its outputs to produce the correct air/fuel ratio.
Variations in the voltage signal from the oxygen sensor serve as air/fuel ratio indicators, changes occur because the oxygen sensor acts as a variable resistor. When oxygen content is low (rich mixture), the voltage signal will be less than 2.5 volts. A lean mixture (high oxygen content), the voltage signal is above 2.5 volts.
The resistance element in the oxygen sensor is a small, titania semiconductor. The titania oxygen sensor must be connected into a voltage network. A 5 volt reference is applied to a fixed resistor (located in the ECU) that is wired in series with the oxygen sensor. The ECU then checks the voltage between the fixed resistor and the oxygen sensor and then relates the voltage to oxygen content.
The oxygen sensor contains a heater in the sensor housing. The heater is a ceramic, resistance-type element that operates on 12 volts supplied through a relay controlled by the ECU. The heater is needed to maintain the titania semiconductor at its operational temperature of approximately 1475 degrees F. (850 degrees C.)
The oxygen sensor heater relay is controlled by the ECU. When the ECU determines high exhaust gas rates and exhaust gas oxygen sensor heating is no longer required, the ECU completes the relay coil ground circuit. When the ground circuit is complete, the relay contacts open, and the exhaust gas oxygen sensor heater is disabled.

Knock Sensor
This sensor is located at the lower left hand side of the cylinder block, just above the oil pan. This sensor provides an input to the ECU when detonation is encountered during engine operation. The ECU will retard ignition timing when the input signal from the knock sensor indicates engine detonation.

Fig. 1 Flywheel tooth identification:

Speed Sensor
The speed sensor is attached to the flywheel housing. This sensor detects TDC, BDC and engine speed by sensing the flywheel teeth as they pass during engine operation. The flywheel has a large trigger tooth and notch located 12 teeth before TDC and BDC. As the small teeth on the flywheel pass the sensor magnetic core, the concentration and collapse of magnetic flux induces a low voltage spikes into the sensor pickup coil winding. These low voltage spikes allow the ECU to count the flywheel teeth as they pass the sensor. When the large trigger tooth on the flywheel passes the sensor magnetic core, a higher voltage spike is induced into the pickup coil winding, indicating to the ECU that TDC or BDC is 12 teeth away. The ignition timing will be advanced or retarded as necessary by the ECU depending on sensor input signals.



Starter Motor Relay
The starter motor relay indicates to the ECU when starter motor is in operation.

Throttle Position Sensor (TPS)
This sensor is mounted to the throttle plate assembly and provides the ECU with input signal indicating throttle position. At idle speed the TPS will provide the ECU with an input signal of approximately 1 volt, indicating throttle is at minimum opening. As the throttle is opened, the voltage signal to the ECU will increase. At wide open throttle the voltage signal will be approximately 5 volts. On models with automatic transmission, a dual TPS is used. The dual TPS will provide throttle opening voltage signals to the ECU and the automatic transmission control unit (TCU).

Battery Voltage
The battery voltage input signal to the ECU is used to ensure proper voltage is being applied to the injectors. The ECU will vary voltage applied to the injectors to compensate for battery voltage fluctuations.

Park/Neutral Switch
This switch is used on models with automatic transmission to provide a signal to the ECU indicating when transmission is in Neutral or Park.

A/C Controls
The A/C control inputs indicate to the ECU when A/C is in the on position and when A/C compressor clutch is engaged. When the compressor clutch is engaged, the ECU will increase engine idle speed.

Sync Pulse
The sync pulse signal is generated by a trigger wheel located in the ignition distributor.