Powertrain Control Module

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

1 - PCM

The Powertrain Control Module (PCM) is a programmed digital microprocessor. The PCM is located in the right front corner of the engine compartment.

OPERATION 

The main function of the PCM is to electrically control and monitor the engine operating systems. The PCM can adapt its programming to meet changing operating conditions. The PCM receives

input signals 

from various switches and sensors. Based on these inputs, the PCM regulates various engine and vehicle operations through different system components. These components are referred to as

PCM Outputs 

The PCM regulates the following Powertrain functions:

• Fuel System - air-fuel ratio
• Ignition Timing
• Idle Speed
• Engine System Controls
• Emission Control Devices
• Charging System
• Speed Control
• Air Conditioning Compressor Clutch Engagement

By monitoring the exhaust oxygen content through the O2 Sensors and all other inputs, the PCM has the ability to fine tune the air handling, fuel control, ignition timing and spark advance settings. This is done to achieve optimum fuel economy combined with low emission engine performance.

The PCM communicates with other system modules over the Controller Area Networks (CAN-FD3 and PRIVATE CAN-FD14).

The PCM will operate in two different modes, Open and Closed Loop.

Open/Closed Loop Operation: 

• Open Loop  - When the engine is first started the PCM operates in Open Loop operation. In Open Loop, the PCM calculates the Air/Fuel ratio based on limited inputs from various sensors. The PCM remains in Open Loop until the engine warms to a predetermined temperature and the O2 sensors begin operating. During Open Loop operation, the PCM still receives all input signals but responds only to a limited amount of inputs based on the algorithms for output control. Inputs from the Oxygen (O2) Sensors and other sensors (depending on the PCM programming) are not monitored during Open Loop modes.
• Closed Loop  - When the necessary operating conditions are met, the PCM goes into Closed Loop operation. In this mode, the PCM calculates the Air/Fuel ratio based on input feedback from a variety of sensors. During Closed Loop operation, the PCM will monitor all inputs and outputs. These inputs indicate to the PCM whether or not the calculated output settings result in the ideal air-fuel ratio. This ratio is 14.7 parts air to 1 part fuel (14.7:1).