General System Description

PURPOSE
The Electronic Engine Control (EEC) maintains an air/fuel mixture as close as possible to the required exhaust emission levels for all operating conditions.

OPERATION
To maintain fuel economy, good driveability, reduced vehicle emissions and during normal operation, the computer monitors various engine sensors and switches. The computer interprets the data in order to control various output devices that effect air intake, amount of fuel injection, fuel injection timing, evaporative emissions, idle-up, deceleration, ignition timing and automatic transaxle lockup operation.

Input/Output Relationships:

INPUTS/OUTPUTS
Individual components function as either input or output devices.

Powertrain Control Module Inputs:

Input devices modify or generate voltage signals that the Powertrain Control Module (PCM) "reads".

Powertrain Control Module Outputs:

Output devices are PCM operated or controlled components.

Not all of these devices are monitored by the on-board diagnostic system. Some input signals come from devices that are not specifically PCM sensor devices.
For example, the A/C amplifier signals the PCM when the air conditioning is turned "ON", for idle speed control (to compensate for the additional load on the engine). In the case of many output devices (relays and solenoids), the PCM output function is simply to make or break the ground circuit to turn a device "ON" or "OFF".