Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Electronic Engine Control (EEC) System: Notes
Overview
The electronic engine control (EEC) system provides optimum control of the engine and transmission through the enhanced capability of the PCM. The EEC system also has an on-board diagnostics monitoring system (OBD II with features and functions to meet federal regulations on exhaust emissions).
The EEC system has two major divisions: hardware and software. The hardware includes the PCM, sensors, switches, actuators, solenoids, and interconnecting terminals. The software in the PCM provides the strategy control for outputs (engine hardware) based on the values of the inputs to the PCM. EEC hardware and software are discussed in this section.
This section contains detailed descriptions of the operation of EEC system input sensors and switches, output actuators, solenoids, relays and connector pins (including other power-ground signals).
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 II strategy, controls the malfunction indicator lamp (MIL), communicates to the WDS or equivalent tester via the data link connector (DLC), allows for Flash Electrically Erasable Programmable Read Only Memory (FEEPROM), provides idle air and fuel trim, and controls Failure Mode Effects Management (FMEM).
Modifications to OBD II Vehicles
Modifications or additions to the vehicle may cause incorrect operation of the OBD II system. Anti-theft systems, cellular telephones and CB radios must be carefully installed. Do not install these devices by tapping into or running wires close to powertrain control system wires or components .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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