Powertrain Control Module (Pcm)

The PCM is a digital computer that controls ignition timing, air/fuel ratio, fuel injector pulse width, ignition coil(s), spark advance, emission control devices, cooling fan, charging system, idle speed, cruise control (if equipped), fuel pump and tachometer. For PCM location, see wiring diagram in the WIRING DIAGRAMS article. PCM uses data from various input sources to control output devices in order to achieve optimum engine performance for all operating conditions.

PCM has voltage converters that convert battery voltage to regulated 5-volt and 8-volt outputs. The 5-volt output powers battery temperature sensor, Camshaft Position (CMP) sensor on some models equipped with Direct Ignition System (DIS) or distributor on some models without DIS, Crankshaft Position (CKP) sensor, Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, logic circuits, Manifold Absolute Pressure (MAP) sensor, Throttle Position (TP) sensor and Vehicle Speed Sensor (VSS) on some models. The 8-volt output is used to power CMP sensor on some models with DIS or distributor on some models without DIS and CKP sensor. The 8-volt output may also be used to power VSS on some models.

NOTE: Components are grouped into 2 categories. The first category, INPUT DEVICES, includes components that control or produce voltage signals monitored by the PCM. The second category, OUTPUT SIGNALS , includes components controlled by the PCM (this is accomplished by the PCM grounding individual circuits).