Chevrolet Citation/Omega/Phoenix/Skylark 1980-1985 Repair Guide

Computer Command Control System

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OPERATION





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Fig. Fig. 1 Computer Command Control (CCC) system parameters



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Fig. Fig. 2 Schematic of the CCC system which is used on all vehicles, except 1980 California models



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Fig. Fig. 3 View of the CCC system components



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Fig. Fig. 4 View of the ECM/PROM assembly, which is a main component of the CCC system



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Fig. Fig. 5 Some of the other system components are the oxygen (O2) sensor ...



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Fig. Fig. 6 ... the coolant sensor and ...



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Fig. Fig. 7 ... a Throttle Position Sensor (TPS)

The Computer Command Control System, installed on all 1981 and later X-Body cars, is basically a modified version of the C-4 system. Its main advantage over its predecessor is that it can monitor and control a larger number of interrelated emission control systems.

This new system can monitor up to 15 various engine/vehicle operating conditions and then use this information to control as many as 9 engine related systems. The "System" is thereby making constant adjustments to maintain good vehicle performance under all normal driving conditions while at the same time allowing the catalytic converter to effectively control the emissions of NO x , HC and CO.

In addition, the system has a built-in diagnostic system that recognizes and identifies possible operational problems and alerts the driver through a "Check Engine" light in the instrument panel. The light will remain "ON" until the problem is corrected. The system also has built-in back-up systems that in most cases of an operational problem will allow for the continued operation of the vehicle in a near normal manner until the repairs can be made.

The CCC system has some components in common with the C-4 system, although they are not interchangeable. These components include the Electronic Control Module (ECM), which, as previously stated, controls many more functions than does its predecessor, an oxygen sensor system, an electronically controlled variable-mixture carburetor, a three-way catalytic converter, throttle position and coolant sensors, a Barometric Pressure Sensor (BARO), a Manifold Absolute Pressure Sensor (MAP) and a "Check Engine" light in the instrument panel.

Components unique to the CCC system include the Air Injection Reaction (AIR) management system, a charcoal canister purge solenoid, EGR valve controls, a vehicle speed sensor (in the instrument panel), a transmission converter clutch solenoid (only on models with automatic transaxle), idle speed control and Electronic Spark Control (ESC).

The ECM, in addition to monitoring sensors and sending out a control signal to the carburetor, also controls the following components or sub-systems: charcoal canister purge control, the AIR system, idle speed, automatic transaxle converter lock-up, distributor ignition timing, the EGR valve, and the air conditioner converter clutch.

The EGR valve control solenoid is activated by the ECM in a fashion similar to that of the charcoal canister purge solenoid described earlier in this section. When the engine is cold, the ECM energizes the solenoid, which blocks the vacuum signal to the EGR valve. When the engine is warm, the ECM de-energizes the solenoid and the vacuum signal is allowed to reach and then activate the EGR valve.

The Transmission Converter Clutch (TCC) lock is controlled by the ECM through an electrical solenoid in the automatic transaxle. When the vehicle speed sensor in the dash signals the ECM that the car has attained the pre-determined speed, the ECM energizes the solenoid which then allows the torque converter to mechanically couple the engine to the transaxle. When the brake pedal is pushed, or during deceleration or passing, etc., the ECM returns the transaxle to fluid drive.

The idle speed control adjusts the idle speed to all particular engine load conditions and will lower the idle under no-load or low-load conditions in order to conserve fuel.

 
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