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3.
Fuel Cut-off Control
•
During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy at
speeds over 970 rpm ('97 - 98 models), 920 rpm ('99 - 00 models).
•
Fuel cut·off action also takes place when engine speed exceeds 6,500 rpm ('97 - 98 models), 6900 rpm ('99 - 00
models), regardless of the position of the throttle valve, to protect the engine from over-rewing.
With
AfT
model, the PCM cuts the fuel at engine speeds over 5,000 rpm when the vehicle is not moving.*2
4.
NC
Compressor Clutch Relay
When the ECM/PCM receives a demand for cooling from the air conditioning system, it delays the compressor from
being energized, and enriches the mixture to assure a smooth transition to the
Ale
mode.
5.
Evaporative Emission (EVAP) Purge Control Solenoid Valve
When the engine coolant temperature is above 154'F (68'C), the ECM/PCM controls the EVAP purge control solenoid
valve which controls vacuum to the EVAP purge control canister.
6.
Alternator Control
The system controls the voltage generated at the alternator in accordance with the electrical load and driving mode,
which reduces the engine load to improve the fuel economy.
PCM Fail-safe/Back-up Functions
1.
Fail·safe Function
When an abnormality occurs in a signal from a sensor, the ECM/PCM ignores that signal and assumes a pre·pro-
grammed value for that sensor that allows the engine to continue to run.
2.
Back-up Function
When an abnormality occurs in the ECM/PCM itself, the fuel injectors are controlled by a back-up circuit independent
of the system in order to permit minimal driving.
3.
Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]
When an abnormality occurs in a signal from a sensor, the ECM/PCM supplies ground for the MIL and stores the DTe
in erasable memory. When the ignition is initially turned on
(11),
the ECM/PCM supplies ground for the MIL for two
seconds to check the MIL bulb condition.
4.
Two Trip Detection Method
To prevent false indications, the Two Trip Detection Method is used for the H02S*', fuel metering-related, idle control
system, ECT sensor and EVAP control system self-diagnostic functions. When an abnormality occurs, the ECM/PCM
stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON
(II)
again,
the ECM/PCM informs the driver by lighting the MIL. However, to ease troubleshooting, this function is cancelled
when you jump the service check connector. The MIL will then blink immediately when an abnormality occurs.
5.
Two (or Three) Driving Cycle Detection Method ('97 model!
A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. If misfir-
ing that increases emissions or EVAP control system malfunction is detected during two consecutive driving cycles,
or TWC deterioration is detected during three consecutive driving cycles, the ECM/PCM turns the MIL on. However, to
ease troubleshooting, this function is cancelled when you jump the service check connector. The MIL will then blink
immediately when an abnormality occurs.
*1: '97 - 98 models
*2: '99 - 00 models
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Table of Contents
Troubleshooting
