Feedback Control System

Computerized Engine Control System:

The Electronic Control Unit contains logic circuits that sense the inputs and apply outputs as required to control emissions and effect smooth engine performance. The control unit controls: Idle Speed, Feedback Control Function, Fuel Cut-off, Exhaust Gas Recirculation, Air Injection, Evaporative Emission Control, Back-up Function.

ECU BACK-UP FUNCTIONS:

1. Fail-Safe Function:
When an abnormality occurs in the signal from a sensor, the control unit ignores that signal and assumes a preprogrammed value that allows the engine to continue to run.
2. Back-up Function:
When an abnormality occurs in the control unit itself, a back up circuit independent of the system permits minimal driving.
3. Self-diagnosis Function ("Check Engine" warning light and LED indicator):
When an abnormality occurs in a signal from a sensor, the control unit lights the "Check Engine" warning light, stores the failure code in an erasable memory location, and indicates the code with a LED on the control unit anytime the ignition is on. When the ignition is initially turned on, the control unit supplies ground for the "Check Engine" warning light for about 2 seconds.