Diesel Electronic Engine Control (EEC) System: Overview

The PCM contains both engine and transmission microprocessors. Operating information, as well as fault information, is communicated between the two processors via controller area network (CAN) communications. Both can be programmed individually, however replacement of the PCM is as an assembly.

Fuel control is accomplished by the PCM and the fuel injection control module (FICM). The two modules communicate operational information via CAN communications.

The electronic control (EC) system provides optimum control of the engine and transmission through the enhanced capability of the PCM. The EC system also has an on-board diagnostics monitoring system (on -board diagnostics) with features and functions to meet federal regulations on exhaust emissions.

The EC system has two major divisions: hardware and software. The hardware includes the PCM, FICM, sensors, switches, actuators, solenoids, and interconnecting terminals. The software in the PCM provides the strategy control for outputs (engine and transmission hardware) based on the values of the inputs to the PCM. EC hardware and software are discussed in this article.

The PCM receives information from a variety of sensor and switch inputs. Based on the strategy and calibration stored within the memory chip, the PCM generates the appropriate output. The system is designed to minimize emissions and optimize fuel economy and driveability. The software strategy controls the basic operation of the engine and transmission, provides the OBD strategy, controls the MIL, communicates to the scan tool via the data link connector (DLC), allows for flash electrically erasable programmable read only memory (FEEPROM), and controls failure mode effects management (FMEM).