Engine Control Module/Powertrain Control Module

The Engine Control Module (ECM) or Powertrain Control Module (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, EGR operation, A/C relay and fuel pump. ECM is used on vehicles equipped with a manual transmission (M/T). PCM is used on vehicles equipped with an automatic transmission (A/T). ECM/PCM is located next to glove box. ECM/PCM uses data from various input sources to control output devices in order to achieve optimum engine performance for all operating conditions. See Fig 1 and Fig 2 .

ECM/PCM has voltage converters that convert battery voltage to regulated 5-volt outputs. The 5-volt output powers Barometric (BARO) pressure sensor, Camshaft Position (CMP) sensor on 2.4L engines equipped with Distributorless Ignition System (DIS) or distributor on 3.0L engines without DIS, Crankshaft Position (CKP) sensor, Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, knock sensor, logic circuits, Manifold Absolute Pressure (MAP) sensor, Output Speed Sensor (OSS) or Vehicle Speed Sensor (VSS), Throttle Position (TP) sensor and Volume Airflow (VAF) sensor.

Fig 1: Computerized Engine Controls (2.4L)

Courtesy of CHRYSLER CORP.

Fig 2: Computerized Engine Controls (3.0L)

Courtesy of CHRYSLER CORP.

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