Eighty-Eight Royale FWD V6-3.8L VIN K (1996)
Engine Control Module: Description and Operation
PCM Inputs
3X REFERENCE PCM INPUT
From the ignition control module, the PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds above 1200 RPM.
The PCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, DTC P1374 will set and the
PCM will use the 18X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 18X reference signal
only.
18X REFERENCE PCM INPUT
From the ignition control module, the PCM uses this signal to calculate engine RPM and crankshaft position at engine speeds below 1200 RPM.
The PCM also uses the pulses on this circuit to initiate injector pulses. If the PCM receives no pulses on this circuit, DTC P0336 will set and the
PCM will use the 3X reference signal circuit at all times for fuel and ignition control. The engine will continue to start and run using the 3X
reference signal only.
AC REFRIGERANT PRESSURE SENSOR Refer to A/C Signal.
AC REQUEST PCM INPUT Refer to A/C Signal.
CRANKSHAFT POSITION (CKP) SENSOR Refer to Crankshaft Position Sensor.
CAMSHAFT POSITION (CMP) SENSOR AND CAM SIGNAL Refer to Camshaft Position Sensor.
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.
ELECTRONIC BRAKE AND TRACTION CONTROL MODULE (EBTCM)
The PCM uses the serial data line (CKT 800) to communicate with various other components and systems within the vehicle.
EGR PINTLE POSITION SENSOR Refer to EGR Valve Position Sensor.
ENGINE OIL LEVEL SENSOR
The oil level is determined by an optical sensor which detects oil level immediately upon powerup. While the engine oil level sensor is
determining oil level, the sensor holds the state of the engine oil level signal at ignition voltage. The amount of time the engine oil level sensor
requires to determine oil level is about 1.5 seconds. After the engine oil level has been determined, the engine oil level sensor will ground the
engine oil level signal for 1 to 2 seconds if oil level is OK; 6 to 10 seconds if oil level is low.
EVAP VACUUM SWITCH Refer to EVAP Purge Solenoid.
FUEL LEVEL SENSOR PCM INPUT
The fuel level sensor input to the PCM is used to determine if the fuel level in the tank is correct to run the EVAP diagnostic tests. To ensure
sufficient volume in the tank to begin the various diagnostic tests, the fuel level must be between 15% and 85%.
FUEL TANK PRESSURE SENSOR
The fuel tank pressure sensor is used to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic routine. Refer to EVAP
Control System for a complete description of the EVAP system.
HEATED OXYGEN SENSORS Refer to Heated Oxygen Sensor.
OIL 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 Soon/Now message after start-up. The PCM will command the Change Oil Soon indicator or Change
Oil Soon/Now message ON after each start-up 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.
