The Mass Air Flow (MAF) sensor is located near the air cleaner.

The sensor measures the mass of air passing through the air intake and generates a voltage signal. The Powertrain Control Module(PCM) receives the voltage generated by the sensor and uses the signal to set fuel injector basepulse width and ignition timing.

The resistance of the sensor decreases as mass air flow increases. Voltage and current flow is increased to maintain the film's temperature and resistivity.

The Intake Air Temperature (IAT) sensor is in the MAF sensor. The IAT sensor is a variable resistor whose resistance changes as the temperature of the air flowing through the air intake changes. The Powertrain Control Module (PCM) uses the IAT sensor input to adjust fuel injector pulse width. When the temperature sensed is cold, the PCM enriches fuel mixture by increasing injector pulse width; as the air warms, the injector pulse width time is shortened.

The throttle position sensor (TPS) mounts on the side of the throttle body and is connected to the throttle blade shaft. The TPS is a variable resistor (potentiometer) whose resistance changes according to the throttle blade shaft position. During acceleration, the TPS resistance decreases; during deceleration, the TPS resistance increases. The TPS also includes an idle position switch. The switch is closed in the idle position. The Powertrain Control Module (PCM) applies a reference voltage to the TPS and then measures the voltage that is present on the TPS signal circuit. The PCM uses the TPS signal to adjust the timing and injector pulse width. The TPS signal along with the MAP sensorsignal is used by the PCM to calculate the engine load.

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the ratio of the air must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio. When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the PCM of the LEAN condition. When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the PCM of theRICH condition.

The PCM determines by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the PCM is unable to perform an accurate air-fuel ratio control. The heated oxygen sensors include a heater which heats the sensing element. The heater is controlled by the PCM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the ratio of the air must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio. When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the PCM of the LEAN condition. When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the PCM of theRICH condition.

The PCM determines by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the PCM is unable to perform an accurate air-fuel ratio control. The heated oxygen sensors include a heater which heats the sensing element. The heater is controlled by the PCM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the ratio of the air must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio. When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the PCM of the LEAN condition. When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the PCM of theRICH condition.

The PCM determines by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the PCM is unable to perform an accurate air-fuel ratio control. The heated oxygen sensors include a heater which heats the sensing element. The heater is controlled by the PCM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the ratio of the air must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio. When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the PCM of the LEAN condition. When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the PCM of theRICH condition.

The PCM determines by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the PCM is unable to perform an accurate air-fuel ratio control. The heated oxygen sensors include a heater which heats the sensing element. The heater is controlled by the PCM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

The fuel injectors are solenoid operated valves that are normally closed. When a fuel injector solenoid is energized (pulsed) the injector needle valve moves, allowing pressurized fuel to pass through the injector and mix with the air entering the engine. Each fuel injector (there is one for each engine cylinder) is mounted in the intake manifold and is positioned to spray fuelinto a cylinder head intake port.

The Powertrain Control Module (PCM) controls injector timing and pulse width (how long the fuel injectors are turned on). The PCM pulses the fuel injectors based on information provided by its network of engine sensors. The PCM uses the crankshaft position sensor to determine when to pulse the injectors. Engine coolant temperature, intake air temperature, air flow and throttle position data are all used by the PCM to calculate injector pulsewidth.

The PCM also uses its network of sensors to determine whether all injectors should be pulsed at the same time (simultaneous injection) or each injector should be pulsed individually (sequential injection). Sequential injection is almost always used during normal engine operation and simultaneous injectionmay be used when the engine is being cranked.

With the ignition switch ON or START, voltage is applied to the ignition coil. High tension leads go to each cylinder from the ignition coil. The ignition coil fires two spark plugs every power stroke (the cylinder under compression and the cylinder on the exhaust stroke). Coil number one fires cylinders 1 and 4. Coil number two fires cylinders 2 and 5. And coil number three firescylinders 3 and 6.

The ignition power transistor, controlled by the Powertrain Control Module (PCM), provides a switching circuit to ground for energizing the primary ignition coils. When a primary ignition coil is energized and deenergized, the secondary coil produces a high voltage spike across the attached spark plugs. At the same time, the tachometer interface (part of the ignition power transistor) provides the PCM and Transaxle Control Module (TCM) with an RPMsignal.

With the ignition switch ON or START, voltage is applied to the ignition coil. High tension leads go to each cylinder from the ignition coil. The ignition coil fires two spark plugs every power stroke (the cylinder under compression and the cylinder on the exhaust stroke). Coil number one fires cylinders 1 and 4. Coil number two fires cylinders 2 and 5. And coil number three firescylinders 3 and 6.

The ignition power transistor, controlled by the Powertrain Control Module (PCM), provides a switching circuit to ground for energizing the primary ignition coils. When a primary ignition coil is energized and deenergized, the secondary coil produces a high voltage spike across the attached spark plugs. At the same time, the tachometer interface (part of the ignition power transistor) provides the PCM and Transaxle Control Module (TCM) with an RPMsignal.

The Hall-effect Crankshaft Position (CKP) sensor consists of a magnet and coil located next to the flywheel. The voltage signal from the CKP sensor allows the Powertrain Control Module (PCM) to determine the engine of theRPM and Crankshaft Position.

The Camshaft Position (CMP) sensor senses the Top Dead Center (TDC) point of the #1 cylinder in the compression stroke. The CMP sensor signalallows the PCM to determine when to operate the fuel injectors.

The PCM compares the waveform of the front oxygen sensor with the waveform of the rear oxygen sensor to determine whether or not catalyst performance has deteriorated. Air-fuel ratio feedback compensation keeps the waveform of the front oxygen sensor repeatedly changing back and forth from rich tolean.

If the catalyst is functioning normally, the waveform of the rear oxygen sensor switches back and forth between rich and lean much more slowly than the waveform of the front oxygen sensor. When both waveforms change at a similarrate, catalyst performance has deteriorated.

The evaporative system reduces hydrocarbon emission by trapping fuel tank vapors until they can be burned as part of the incoming fuel charge. Evaporating fuel is stored in a charcoal canister until it can be flushedinto the intake manifold.

The vehicle speed sensor outputs a pulse signal while the vehicle is driven.

The powertrain control module checks whether the pulse signal is present.

The MAP sensor is essentially a strain gauge used to measure the pressure in the surge tank. Inside the sensor is a metal diaphragm with a small wire attached. The diaphragm flexes according to changes in pressure. When the diaphragm flexes, the wire attached to it stretches, changing the resistance of the wire. The Powertrain Control Module (PCM) applies five volts to the MAP sensor and measures the voltage drop across the sensor. The sensor output is in volts and as pressure decreases, the voltage drop across the sensorincreases.

The Engine Coolant Temperature (ECT) sensor is located in a coolant passage of the cylinder head. The ECT sensor is a variable resistor whose resistance changes as the temperature of the engine coolant flowing past the sensor changes. When the coolant temperature is low, the sensor resistance is high; when the coolant temperature is high, the sensor resistance is low. The Powertrain Control Module (PCM) checks ECT voltage fifty times per second and uses the information to help adjust the fuel injector pulse width and ignition timing. When the temperature sensed is very cold, the PCM enrichesthe fuel mixture.