Chevrolet Chevette/1000 1976-1988 Repair Guide

Computer Command Control (CCC) System



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Fig. Fig. 1The CCC system test terminal ground is located under the instrument panel

The CCC system is used on all 1981 and later carbureted engines. The CCC has many components in common with the C-4 System (although they should never be interchanged between systems). These include the Electronic Control Module (ECM), which is capable of monitoring and adjusting more sensors and components than the ECM used on the C-4 System, an oxygen sensor, an electronically controlled variable-mixture carburetor, a three-way catalytic converter, throttle position and coolant sensors, a barometric pressure (BARO) sensor, a Manifold Absolute Pressure (MAP) sensor, a check engine light for the instrument cluster.

Components used almost exclusively by the CCC system include the Air Injection Reaction (AIR) Management System, charcoal canister purge solenoid, EGR valve control, vehicle speed sensor (located in the instrument cluster), transmission torque converter clutch solenoid (automatic transmission models only), idle speed control, and Early Fuel Evaporative (EFE) system.

See the operation descriptions under C-4 System for those components (except the ECM) the CCC System shares with the C-4 System.

The CCC System ECM, in addition to monitoring sensors and sending a control signal to the carburetor, also control the following components or sub-systems; charcoal canister purge, AIR Management System, idle speed control, automatic transmission converter lockup, distributor ignition timing, EGR valve control, EFE control and the air conditioner compressor clutch operation. The CCC ECM is equipped with a PROM assembly similar to the one used in the C-4 ECM. See above for description.

The AIR Management System is an emission control which provides additional oxygen either to the catalyst or cylinder head ports (in some cases exhaust manifold). An AIR Management System, composed of an air switching valve and/or an air control valve, controls the air pump flow and is itself controlled by the ECM. A complete description of the AIR System is given elsewhere in this unit repair section. The major difference between the CCC AIR System and the systems used on other cars is that the flow of air from the air pump is controlled electrically by the ECM, rather than by vacuum signal.

The charcoal canister purge control is an electrically operated solenoid valve controlled by the ECM. When energized, the purge control solenoid blocks vacuum from reaching the canister purge valve. When the ECM de-energizes the purge control solenoid, vacuum is allowed to reach the canister and operate the purge valve. This releases the fuel vapors collected in the canister and into the induction system.

The EGR valve control solenoid is activated by the ECM in similar fashion to the canister purge solenoid. 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 activate the EGR valve.

The Early Fuel Evaporative (EFE) System is used on some engines to provide rapid heat to the engine induction system to promote smooth start-up and operation. There are two types of systems; vacuum servo and electrically heated. They use different means to achieve the same end, which is to pre-heat the incoming air/fuel mixture. They are controlled by the ECM.

The Transmission Converter Clutch (TCC) lock is controlled by the ECM through an electrical solenoid in the automatic transmission. When the vehicle speed sensor in the instrument panel signals the ECM that the vehicle has reached the correct road speed, the ECM energizes the solenoid which allows the torque converter to mechanically couple the engine to the transmission. When the brake pedal is pushed or during deceleration, passing, etc., the ECM returns the transmission to fluid drive.

The idle speed control adjusts the idle speed to load conditions, and will lower the idle speed under no-load or low-load conditions to conserve gasoline.