Viper V10-488 8.0L (1992)
Engine Control Module: Description and Operation
General Operation
As input signals to the Powertrain Control Module (PCM) change, The PCM adjusts its response that it sends to the output devices. For example,
the PCM must calculate a different injector pulse width and ignition timing for idle than it does for Wide Open Throttle (WOT).
The PCM also instructs the Ignition Control Module (ICM) to change ignition timing to compensate for different operating conditions.
There are eight modes of operation that determine how the PCM responds to the various input signals.
-
Ignition switch ON
-
Engine start-up
-
Engine warm-up
-
Idle/Cruise
-
Acceleration
-
Deceleration
-
Wide Open Throttle (WOT)
-
Ignition switch OFF
Modes of operation are separated into two different types:
-
OPEN LOOP: Ignition switch ON, engine start-up (CRANK), engine warm-up, wide open throttle, and ignition switch OFF modes.
-
CLOSED LOOP: Cruise (Idle), deceleration, and Acceleration modes, with the engine at operating temperature modes.
During OPEN LOOP modes the PCM receives input signals and responds only to preset PCM programming. Input from the oxygen (02) sensor is
not monitored during OPEN LOOP modes.
During CLOSED LOOP modes the PCM monitors the oxygen sensor input. This input indicates to the PCM whether or not the calculated injector
pulse width results in the ideal air/fuel ratio of 14.7 parts of air to 1 part of fuel. By monitoring the exhaust oxygen content, using the oxygen
sensor, the PCM can "fine tune" the injector pulse width to achieve optimum fuel economy and performance combined with low emission levels.
