Information Sensors/Switches

3X REFERENCE PCM INPUT
The PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds above 1200 RPM.

18X REFERENCE PCM INPUT
The PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds below 1200 RPM.

A/C REFRIGERANT PRESSURE SENSOR
The PCM uses this information to adjust the idle air control valve to compensate for the higher engine loads present with high A/C refrigerant pressures and to control the cooling fans.

AC REQUEST PCM INPUT
The A/C request signal indicates to the PCM that an A/C mode is selected at the A/C control head. The PCM uses this information 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.

CRANKSHAFT POSITION (CKP) SENSOR
The crankshaft position sensor provides a signal used by the ignition control module to calculate ignition sequence. The ignition control module also uses the crankshaft position sensor signals to initiate 18X and 3X reference pulses which the PCM uses as reference to calculate RPM and crankshaft position.

CAMSHAFT POSITION (CMP) SENSOR AND CAM SIGNAL
The camshaft position sensor sends a cam signal to the PCM which uses it as a sync pulse to trigger the injectors in proper sequence.

TRACTION CONTROL DELIVERED TORQUE CIRCUIT
The PCM sends a PWM signal to the Electronic Brake and Traction Control Module (EBTCM) on the delivered torque circuit informing the EBTCM of response made to the desired torque signal. A problem with the delivered torque circuit should cause an ABS/TCS DTC to set and traction control to be disabled.

TRACTION CONTROL DESIRED TORQUE CIRCUIT
The Electronic Brake and Traction Control Module (EBTCM) controls the PWM signal on the Desired Torque circuit while monitoring the wheel speed sensors to detect slippage. The PCM monitors the PWM signal and reduces engine torque as needed by retarding ignition timing, decreasing boost duty cycle, increasing air/fuel ratio, or, in severe cases, shutting OFF up to three fuel injectors. A problem with the Desired Torque circuit should cause PCM DTC P1571 and an ABS/TCS DTC to set and traction control to be disabled.

ELECTRONIC BRAKE AND TRACTION CONTROL MODULE (EBTCM) I ELECTRONIC BRAKE CONTROL MODULE (EBCM) - PCM SERIAL DATA
The PCM uses the serial data line to communicate with various other components and systems within the vehicle. If the PCM does not receive data from the Electronic Brake and Traction Control Module (EBTCM), the PCM will store DTC P1573 indicating loss of communication with the ABS/TCS system. The PCM also receives rough road information from the EBTCM / EBCM on the serial data circuit. The PCM uses the rough road information to enhance the misfire diagnostic by detecting crankshaft speed variations caused by driving on rough road surfaces.

This allows false misfire information to be rejected. The EBTCM I EBCM calculates rough road information by monitoring the ABS wheel speed sensors. If a malfunction occurs which does not allow the EBTCM / EBCM to transmit correct rough road information to the PCM while a misfire DTC is requesting the MIL, DTC P1380 will set.

Under certain conditions, the PCM has the ability to request the EBTCM to shut OFF traction control via serial data. The following DTCs will cause traction control to be disabled, an ABS/TCS DTC to be set, and the Traction OFF lamp to be illuminated:
^ DTC P0101 - Mass Air Flow System Performance
^ DTC POlO2 - Mass Air Flow Sensor Circuit Low Frequency
^ DTC POlO3 - Mass Air Flow Sensor Circuit High Frequency
^ DTC P0171 - Fuel Trim System Lean
^ DTC P0172 - Fuel Trim System Rich
^ DTC P0300 - Engine Misfire Detected
^ DTC P0336 - 18x Reference Signal Circuit
^ DTC P0341 - Camshaft Position Sensor Performance
^ DTC Pl2OO - Injector Control Circuit
^ DTC P1374 - 3X Reference Circuit

ENGINE COOLANT TEMPERATURE SENSOR
Engine coolant temperature affects most systems the PCM controls.

EGR PINTLE POSITION SENSOR
The PCM monitors the EGR valve pintle position input to ensure that the valve responds properly to commands from the PCM and to detect a fault if the pintle position sensor and control circuits are open or shorted.

ENGINE OIL LEVEL SWITCH
The Engine Oil Level (EOL) switch is a simple float switch that is grounded when the engine oil level is OK.

EVAP VACUUM SWITCH
The EVAP Vacuum Switch is used by the PCM to monitor EVAP canister purge solenoid operation and purge system integrity.

FUEL CONTROL HEATED OXYGEN SENSORS
The fuel control Heated Oxygen Sensor (HO2S 1) is mounted in the exhaust manifolds where it can monitor the oxygen content of the exhaust gas stream. The oxygen present in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from approximately 100 mV (high oxygen content - lean mixture) to 900 mV (low oxygen content - rich mixture). The heated oxygen sensor voltage can be monitored with a scan tool. By monitoring the voltage output of the oxygen sensor, the PCM calculates what fuel mixture command to give to the injectors (lean mixture-low HO2S voltage = rich command, rich mixture-high HO2S voltage = lean command).

INTAKE AIR TEMPERATURE (IAT) SENSOR
The IAT sensor signal is used to adjust spark timing according to incoming air density.

0IL LIFE MONITOR RESET SWITCH INPUT
To determine the engine oil life remaining, the PCM monitors engine coolant temperature, the number of crankshaft revolutions, vehicle speed, engine speed, and calculated oil temperature. When the PCM determines that the engine oil is near the end of its useful life, it will command the cluster via serial data (CKT 800) to illuminate the Change Oil Soon indicator or Change Oil SooniNow message affer startup.

The PCM will command the Change Oil Soon indicator or Change Oil SooniNow message ON after each startup until the engine oil life monitor is reset by grounding the Oil Life Monitor reset circuit through the oil life monitor reset switch for longer than 5 seconds.

REFERENCE LOW
This is a ground circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only through the ignition control module. Although this circuit is electrically connected to the PCM, it is not connected to ground at the PCM. The PCM compares voltage pulses on the 18X and 3X reference input circuits to any on this circuit, ignoring pulses that appear on both. If the circuit is open, or connected to ground at the PCM, it may cause poor engine performance and possibly a MIL with no DTC set.

KNOCK SENSORS
The knock sensor detects abnormal vibration (spark knocking) in the engine. The sensor is mounted in the engine block near the cylinders. The sensor produces an AC output voltage which increases with the severity of the knock. This signal voltage inputs to the Powertrain Control Module (PCM). The PCM then adjusts Ignition Control (IC) timing to reduce spark knock.

THE MASS AIR FLOW (MAF) SENSOR
The Mass Air Flow (MAF) sensor measures the amount of air which passes through the throttle body. The PCM uses this information to determine the operating condition of the engine, to control fuel delivery.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum).

TCC BRAKE SWITCH
The TCC brake switch signal indicates when the brake pedal is applied. The TCC brake switch information is used by the PCM mainly to control the transmission torque converter clutch.

TRANSMISSION TEMPERATURE SENSOR
The transmission fluid temperature sensor is a thermistor which changes value based on the temperature of the transmission fluid.

THROTTLE POSITION (TP) SENSOR
The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the PCM calculates throttle position.

TRANSAXLE RANGE SWITCH
The Transaxle Range Switch is part of the Transaxle Park/Neutral Position (PNP) switch mounted on the transaxle manual shaft. The 4 inputs from the transaxle range switch indicate to the PCM which position is selected by the Transaxle selector lever. This information is used for transmission shift control, ignition timing, EVAP canister purge, EGR and IAC valve operation. The combination of the four transaxle range input states determine the PCM commanded shift pattern. The input voltage level at the PCM is high (B+) when the transaxle range switch is open and low when the switch is closed to ground. The state of each input is available for display on the scan tool. The four parameters represent transaxle range switch Parity, A, B, and C inputs respectively.