Powertrain Control Module (Pcm)

The Powertrain Control Module (PCM) is a preprogrammed, dual microprocessor digital computer that receives various signals from engine sensors and provides the necessary signals to control engine sub-systems. The PCM has a voltage converter that converts battery voltage to regulated 5-volt or 8-volt outputs. The regulated 5-volt output is used to power Manifold Absolute Pressure (MAP) sensor, Throttle Position (TP) sensor and logic circuits. The regulated 8-volt output is used to power crankshaft position sensor and camshaft position sensor located in distributor.

The ignition and fuel injection systems are controlled by the PCM. Based on present engine operating conditions, the PCM is programmed to provide a precise amount of fuel and the correct ignition timing to meet existing engine speed and load requirements.

The PCM adjusts ignition timing based on inputs it receives from camshaft position sensor, MAP sensor, coolant temperature sensor, throttle position sensor, vehicle speed sensor, transmission gear selection (automatic transmissions only) and brake switch.

The PCM adjusts idle speed based on inputs it receives from throttle position sensor, vehicle speed sensor, transmission gear selection (automatic transmissions only), A/C clutch switch and brake switch.

The PCM also controls the speed (cruise) control system and generator charge rate by controlling the generator field.

NOTE: Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals that are monitored by the PCM. The second category covers OUTPUT SIGNALS, which are components controlled by the PCM.