Engine Control Module (ECM)/ Powertrain Control Module (Pcm)

NOTE: Engine Control Module (ECM) is used on vehicles equipped with a manual transmission. Powertrain Control Module (PCM) is used on vehicles equipped with an automatic transmission. ECM will be referred to as a PCM.

Computerized engine controls are used to control fuel, ignition and emission control systems. Powertrain Control Module (PCM) receives input signals from various sensors and components. PCM then compares each signal with a preprogrammed parameter in its memory. Based on this comparison, output signals are then adjusted to allow vehicle to perform optimally under all operating conditions.

If an abnormality occurs in a sensor signal, PCM ignores that signal and assumes a preprogrammed value for that sensor. This allows engine to continue to run. If an abnormality occurs in PCM, fuel injectors are controlled by a back-up circuit independent of PCM system to allow minimal engine operation. If an abnormality occurs in a sensor signal, PCM grounds Malfunction Indicator Lamp (MIL) and stores DTC in erasable memory. When ignition is initially turned on, PCM supplies a ground to MIL for 2 seconds to check MIL bulb condition.

To prevent false indications, 2-trip detection method is used for HO2S, fuel metering-related, idle control system, ECT sensor, EGR system and EVAP control system self-diagnostic function. When an abnormality occurs, PCM stores DTC in memory. When same abnormality reoccurs, after ignition switch is turned off and back on, PCM informs driver by illuminating MIL. To help ease troubleshooting, 2-trip detection method is cancelled when service check connector is jumped. MIL will blink immediately when an abnormality occurs.

Civic is equipped with a 2 or 3 driving cycle detection method. In a 2 or 3 driving cycle detection method, if misfiring that increases emission is detected during 2 consecutive driving cycles, or Three-Way Catalytic (TWC) converter deterioration is detected during three consecutive driving cycles, PCM illuminates MIL. A driving cycle consists of starting engine, beginning closed loop operation and turning engine off. To help ease troubleshooting, 2 or 3 driving cycle detection method is cancelled when service check connector is jumped. MIL will blink immediately when an abnormality occurs.

NOTE: Components are grouped into 2 categories. First category covers INPUT DEVICES, which control or produce voltage signals monitored by PCM. Second category is OUTPUT SIGNALS, which are components controlled by PCM.