Powertrain Control Module (Pcm)

NOTE: All models except Millenia 2.3L and 626 2.0L M/T use a Powertrain Control Module (PCM). Millenia 2.3L and 626 2.0L M/T use an Engine Control Module (ECM). For purpose of this article, all references to PCM include ECM unless otherwise specified.

The PCM, through various input sensors, monitors battery voltage, engine RPM, intake air volume, cranking signal, camshaft position, crankshaft position, intake air temperature, radiator and engine coolant temperatures, exhaust oxygen content, throttle position, EGR valve position, atmospheric pressure, gearshift lever position, clutch engagement, vehicle speed, braking, power steering operation, and A/C compressor operation.

PCM utilizes this input information to control fuel injection system and operation of other output devices. Spark timing is also controlled by PCM.

PCM has a built-in fail-safe mechanism. If a fault occurs while driving, PCM will substitute preprogrammed values. Driving performance will be affected, but vehicle may still be driven.

PCM has a self-diagnostic function, which allows module to store diagnostic trouble codes in its memory. A Malfunction Indicator Light (MIL), located on instrument cluster, informs driver of system problems.

ECM/PCM LOCATIONS

Application	Location
B2500, B3000 & B4000	Right Rear Of Engine Compartment
Miata	Below Center Of Instrument Panel
Millenia	Below Center Of Instrument Panel
MPV	On Floor, Behind Glove Box
Protege	Below Center Of Instrument Panel
626	Below Front Of Center Console

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