General System Description

Fig. 2 Oxygen sensor installation:

Fig. 3 Engine coolant thermal switch installation:

Fig. 4 Micro switch installation:

Fig. 5 Clutch engagement switch installation:

Fig. 6 High altitude compensator (barometric pressure) & engine compartment thermal switch installation:

The ECM is located behind the instrument panel to the left of the steering wheel, and is connected to the CCEC system controls and sensors through a specially constructed wiring harness. The ECM controls CCEC system operation through a group of solenoids and vacuum switching valves based on parameters programmed into an internal memory and information supplied by engine and vehicle sensors. The ECM controls system operation based on the following information:
Exhaust oxygen content (air/fuel mixture) is monitored by an exhaust manifold mounted oxygen sensor, Fig. 2.
Engine coolant temperature is sensed by an intake manifold mounted thermal switch, Fig. 3.
Throttle position is monitored by Wide Open Throttle (WOT) and idle micro switches mounted on the carburetor, Fig. 4.
Engine speed is computed based on pulse signals transmitted from the electronic ignition system. On manual transmission models, clutch engagement is monitored by a switch located above the clutch pedal, Fig. 5. The switch is open when the clutch is engaged (pedal released), and closed when the clutch pedal is depressed.
The ECM senses electrical loads to provide idle speed compensation for models with manual transmission. This allows the ECM to raise idle speed through the idle-up compensator when the headlamps, engine cooling fan, rear defogger or heater fan are operated.
The ECM monitors barometric pressure and ambient air temperature through switches mounted in the engine compartment, Fig. 6. The high altitude compensator (barometric pressure switch) and ambient temperature switch allow the ECM to adjust air/fuel mixtures based on vehicle operating conditions. The ECM provides richer mixtures for low altitude and/or low temperature operation, and leaner mixtures for high temperature and/or high altitude operation.