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3.
Fuel Cut-off Control
. Du ring dece leration with the th rottle va lve closed, cu rrent to the fuel injectors is cutoffto improvefuel economyat
speeds over following rpm:
.
B'1881 engine: 970 rpm {Canada model: 1.050 rpm)
.
B 1 8 C 1 e n g i n e : 9 7 0 r p m { C a n a d a m o d e l : 1 . 0 5 0 r p m )
.
818C5 engine: 1,300 rpm (Canada model: 1,400 rpm)
. F u e l c u t - o f f a c t i o n a l s o t a k e s p l a c e w h e n e n g i n e s p e e d e x c e e d s 7 , 0 0 0 r p m ( B ' 1 8 8 1 e n g i n e ) , 8 . 1 0 0 r p m ( 8 1 8 C 1
engine) or 8,600 rpm (818C5 engine), regardless ol the position of the thronle valve, to protect the engine from
over-revving.
A,,/C ComDressor Clutch Relav
When the ECM receives a demand for cooling from the air conditioning system, it delays the compressor from being
energized, and enriches the mixture to assure smooth transition to the A,/C mode.
Evaporative Emission (EVAP) Purge Control Solenoid Valve
When the engine coolanl temperature is above '154'F (68'C) and the air conditioner on. the ECM controls the EVAP
purge control solenoid valve which controls vacuum to the EVAP purge control canister.
Intake Air Eypass (lAB) Control Solenoid Valve*a
When the engine rpm is below 5,750 rpm, rhe IAB control solenoid valve is activated by a signal from the ECM, intake
air flows through the long intake path, then high torque is delivered. At speeds higher than 5,750 rpm, the solenoid
valve is deactivated by the ECM, and intake air flows through the short intake path in order to reduce the resistance in
airflow.
Sell-diagnosis Function lMalfunction Indicator Lamp {MlL)l
When an abnormality occurs in a signal from a sensor, the ECM supplies ground for the MIL and stores the code in
erasable memory. When the ignition is initially turned on, the ECM supplies ground for the N4lL tor two seconds to
c h e c k t h e M I L b u l b c o n d i t i o n .
Two Driving Cycle Detection Method
To prevent false indications, the Two Driving Cycle Detection Method is used for the HO2S, fuel metering-related, idle
control system, ECT sensor, TWC and EVAP control system and other self-diagnostic functions, When an abnormality
occurs, the ECM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF
a n d O N ( l l ) a g a i n , t h e E C M i n f o r m s t h e d r i v e r b y l i g h t i n g t h e M l L .
However, to ease troubleshooting, this function is cancelled when you shon the service check connector. The MIL will
then blink immediately when an abnormality occurs.
4.
5 .
6 .
3.
4.
ECM Fail-safe/8ack.up F0nctions
1. Fail-sate Function
When an abnormality occurs in a signal from a sensor, the ECM ignores that signal and assumes a pre-programmed
value for that sensor that allows the enqine to continue to run.
2.
Back-uo Function
When an abnormality occurs in the ECM itself, the fuel injectors are controlled by a back-up circuit independent of the
system in order to permit minimal driving.
11 -4 9
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Table of Contents
Troubleshooting
