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◆ Engine ECU
ECU receives and deals with the engine state signal s which is inputted by each sensor,
and drive each actuator work . It enable s the engine work a ccording to establi shed proc edure
and insures the wel l motivity、fuel economy and drain performance.
Engin e computer is installed
ECU（EMS）Engine
at the passenger side
Figure9 -3 Engine ECU
Fau lt descri ption：
Idle speed no t stable、 can not well accelerate、 can not start、 idle speed is too
high、the exhaust e xceeds the standar d、 starts difficult、 A/C invalidation、 fuel in jector
control in validation、 flameout and etc.
Trouble Analysis：
（ 1） The over loadi ng of outer conne ct set re sults in the burn of ECU inner
components, which leads to i nvalidation.
（2）Water gets into t he ECU and results in the rus t in the line board.
Figure9- 4 Diagn osis plu gs
Troubleshoot：
（1） （con nect the plug） u se the e ngine da ta K wir e to read engine fault
record
Start the ignition switch, use the engine data K wire （the standard diagnosis plug 7# pin )
ground （that's to connect the 4# and 7# pin of diagnosis plug with a lead） over 2.5s, if there is
DTC in the ECU fault memorizer, the engine fault lamp will output the flash code, that's P-
CODE. For example: the flashing of P0203 is : flash 10 times continuously-intermission-flash 2
times continuously-intermission-flash 10 times continuously-intermission-flash 3 times
continuously.
（ 2） （ Remove the plug） check whether the ECU connect lines are well, and
whether the ECU power、ground is normal.
（ 3） Check whether the working of outer sensor is normal, whether the output
signal is creditable and whether the line is well.
（4）Check whether the working of actuator is normal and whether the line is well.
（5）Finally replace the ECU to test.
◆Input sign al
The inst allation po sition
（1）Air Flow Meter
of engin e computer
The air flow mete r（ MAF） sensor m easures the volum e of air that inhal ed into th e
engine. Engine control module（ ECM）uses the da ta to calc ulate the spout tim e、ignitio n
timin g and engine load.
Air flow me ter
（Only for 2. 0L engine）
Trouble analysis：
Troubleshoot ：
Static st ate test（zero flu x test）：
The 1st pin is air intake temperatur e pressure sensor, connectin g to the 42nd pin of
ECU; the 3rd pin grou nds and connects to the 17 th pin of ECU;the 4th pin inputs 5 V
refer ence volta ge, and c onnect to 33rd pin of ECU; the 2nd pin input s 14V rati ng voltag e;
the 5 th pin is output vo ltage, and connects to the 37 th pin of ECU.
Check the output voltage of 5th pin, if it is over 1.0 25V, the n the sen sor will be
disqualification.
Dynami c test：
emission analyzer and c heck the performan ce in the two working cond ition.
A ir intake te mperature sensor
（Only for 1.6 L engine）
Remark：There is no air flow meter in t he 1.6L engine elctronic
control system,and what instead is the air temperatur e sensor.
Figure9 -5 Air f low met er and its circuit d iagram
Sensor invalidation result from the pollution of dust、oil and water.
If it is p rimarily diagnosed as the s ensor's t rouble, c onnect th e
To main r elay
2
Air flow meter
3
1
5
4
1 7
42
37
33
EC U
15
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