To control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The PCM has the ability to monitor this process using the Bank 1 Sensor 2 heated oxygen sensor. The Bank 1 Sensor 2 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three-way catalytic converter. If the catalyst is operating efficiently, the Bank 1 Sensor 1 sensor will produce a far more active signal than that produced by the Bank 1 Sensor 2 sensor.

The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 Sensor 2 main function is catalyst monitoring, it also has a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the PCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring.

The Throttle Position (TP) sensor is a potentiometer. The TP sensor is connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the PCM calculates throttle position. As the throttle valve angle is changed (accelerator pedal moved), the TP sensor signal also changes. At a closed throttle position, the output of the TP sensor is low. As the throttle valve opens, the output increases so that at Wide Open Throttle (WOT), the output voltage should be above 4.0 volts.

The PCM calculates fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor may cause intermittent bursts of fuel from an injector. This may cause an unstable idle because the PCM detects the throttle is moving.

When the PCM detects a malfunction with the TP sensor circuits, the following DTCs will set:

The Fuel Pressure sensor is a three wire strain gauge sensor much like that of the common MAP sensor. However, this sensor has very different electrical characteristics due to it's pressure differential design. The sensor measures the difference between the air pressure (or vacuum) in the fuel tank and the outside air pressure.

The sensor mounts at the top of the fuel tank sending unit. A three wire electrical harness connects it to the PCM. The PCM supplies a 5 volt reference voltage and a ground to the sensor. The sensor will return a voltage between 0.1 and 4.9 volts.

The Knock Sensor (KS) system is used to detect engine detonation. The PCM will retard the spark timing based on the signals from the KS module. The Knock Sensors produce an AC voltage that is sent to the KS module. The amount of AC voltage produced is proportional to the amount of knock.

An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensors will produce an AC voltage signal from this Noise. When an engine is operating, the PCM will learn the minimum and maximum frequency of the noise the engine produces. When the PCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set.

The A/C request circuit signals the PCM when an A/C mode is selected at the A/C control head. The PCM uses this information to enable the A/C compressor clutch and to adjust the idle speed before turning ON the A/C clutch. If this signal is not available to the PCM, the A/C compressor will be inoperative.

Refer to A/C Clutch Circuit Diagnosis for A/C wiring diagrams and diagnosis of A/C electrical system.

The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the PCM how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse.

The VSS produces an AC voltage signal that increases with vehicle speed. The PCM processes this signal and sends it to the following components:

The crankshaft position sensor provides the PCM with crankshaft speed and crankshaft position. The PCM utilizes this information to determine if an engine Misfire is present. The PCM monitors the CKP sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the PCM detects a misfire, a DTC P0300 will set.

The Camshaft Position (CMP) sensor is used to indicate the camshaft position so the Powertrain Control Module (PCM) can determine which cylinder is misfiring when misfire is present. Whenever the PCM receives an intermittent signal from the CMP, then the CMP Resync Counter will increment. In order to set a DTC, the PCM must see a minimum number of resyncs within a maximum number of resyncs within a maximum time.