DESCRIPTION
The Computer Controlled Emission (CCE) system is a computerized emission control system. The CCE monitors engine operation to lower exhaust emissions. The Electronic Control Unit (ECU) is the "brain" of the CCE system.
OPERATION
Note. This article briefly describes the CCE system. Each emissions system component is thoroughly covered within individual articles in this section.
The CCE system consists of various sensors and switches that provide the ECU with engine operating conditions. From this information, the ECU issues electrical command signals to vacuum valves, solenoids or other devices. The following systems are controlled by the ECU
FUEL EVAPORATION SYSTEM
The ECU monitors coolant temperature and engine speed. It then compares these inputs with a preprogrammed memory and properly routes fuel vapors.
AIR INJECTION WITH FEEDBACK
Some Toyota models are equipped with an electronically controlled air injection system. This system helps control air/fuel ratio.
The ECU receives information from an oxygen sensor, catalytic converter temperature sensor and coolant temperature sensor. Depending upon coolant temperature, converter temperature and oxygen content of exhaust gases, the ECU directs additional air into the intake manifold or catalytic converter.
AIR BLEED WITH FEEDBACK
On some Toyota models, the ECU monitors oxygen content of exhaust gases with an oxygen sensor. When oxygen content is high, the air bleed passage is closed, allowing a richer mixture. When oxygen content is low, the air bleed passage is opened to allow more air into intake manifold.
EXHAUST GAS RECIRCULATION (EGR)
Some Toyota models are equipped with an electronically controlled EGR system. The ECU monitors engine speed and engine coolant temperature to determine correct time to allow EGR flow.
DECELERATION FUEL CUT SYSTEM
Some Toyota models are equipped with an electronically controlled deceleration fuel cut system. The ECU monitors engine speed to control the fuel cut system during deceleration.
COLD MIXTURE HEATER
All models are equipped with cold mixture heater. When coolant temperature is low, ECU activates a heater in the intake manifold which warms air/fuel mixture. This system promotes starting in cold weather.
DIAGNOSIS & TESTING
No diagnostic or testing information for the ECU is available.
