Impco HHI, Руководство по обслуживанию

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CATALYTIC CONVERTER
The Catalytic Converter is a component of the
emissions system which is designed and cali-
brated to meet the emission standards in effect
for 2007-2009 model year.
The exhaust gases pass through the honeycomb
catalyst which is coated with a mixture of metals
(such as platinum, palladium, and rhodium) to
oxidize and reduce CO, HC and
NOX emission
gases.
Catalytic Converter/Muffler
ENGINE CONTROL MODULE
To obtain maximum effect from the catalyst and
accurate control of the air fuel ratio, the emission
certi
fied engine is equipped with an onboard
computer or Engine Control Module (ECM). The
ECM is a 32 bit controller which receives input
data from sensors mounted to the engine and fuel
system and then outputs various signals to con-
trol engine operation.
Engine Control Module (ECM)
One speci fic function of the controller is to main-
tain a closed loop fuel control which is
accomplished by use of the Heated Exhaust Gas
Oxygen sensor (HEGO) mounted in the exhaust
system. The HEGO sensor sends a voltage sig-
nal to the controller which then outputs signals to
the EPR to change the amount of fuel being deli-
vered from the regulator or mixer to the engine.
The controller also performs diagnostic functions
on the fuel system and noti
fies the operator of
engine malfunctions by turning on a Malfunction
Indicator Light (MIL) mounted in the dash. Mal-
functions in the system are identi
fied by a
Diagnostic Trouble Code (DTC) number. In addi-
tion to notifying the operator of the malfunction in
the system, the controller also stores the informa-
tion about the malfunction in its memory. A
technician can than utilize a computerized diag-
nostic scan tool to retrieve the stored diagnostic
code and by using the diagnostic charts in this
manual to determine the cause of the malfunc-
tion. In the event a technician does not have the
computerized diagnostic tool, the MIL light can be
used to identify the diagnostic code to activate
the “blink” feature and count the number of blinks
to determine the diagnostic code number to lo-
cate the fault in the system.
HEATED EXHAUST GAS OXYGEN SENSORS
The Heated Exhaust Gas Oxygen (HEGO) Sen-
sors are mounted in the exhaust system, one
upstream and one downstream of the catalytic
converter. The HEGO sensors are used to
measure the amount of oxygen present in the ex-
haust stream to determine whether the fuel air
ratio is to rich or to lean. It then communicates
this measurement to the ECM. If the HEGO sen-
sor signal indicates that the exhaust stream is too
rich, the ECM will decrease or lean the fuel mix-
ture during engine operation. If the mixture is too
lean, the ECM will richen the mixture. If the ECM
determines that a rich or lean condition is present
for an extended period of time which cannot be
corrected, the ECM will set a diagnostic code and
turn on the MIL light in the dash.
By monitoring output from the sensor upstream
and the sensor downstream of the catalytic con-
verter, the ECM can determine the performance
of the converter.