Grand Cherokee 2WD V6-3.7L (2008)
Engine Control Module: Description and Operation
Powertrain Control Module - Description
Powertrain Control Module (PCM)
POWERTRAIN CONTROL MODULE (PCM)
The PCM (1) is attached to the right-front inner fender located in the engine compartment.
Modes Of Operation
MODES OF OPERATION
As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices.
The PCM will operate in two different modes: Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S)
sensors is not monitored during Open Loop modes.
During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated
injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the
O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine
The fuel injection system has the following modes of operation:
Ignition switch ON
Engine start-up (crank)
Wide open throttle (WOT)
Ignition switch OFF
The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration and wide open throttle modes are Open Loop modes. The
idle and cruise modes, (with the engine at operating temperature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE