Before Diagnosis - SSANGYONG 2004 Rexton 2.7XDi Workshop Manual

DI04-18

Before Diagnosis

The base of making diagnosis on the EGR related system is the inspection on the connections of the vacuum hoses in
related system as the first priority. When abnormal condition occurs with the EGR system, the basic approach is, as
described in prior sentence, making detail inspections of vacuum circuits of each system before connecting the scan
tool or vacuum tester. It is necessary to manually check on the connections if there are any slacks or loose circuits even
if the visual inspection shows vacuum hose as being connected. If there are not any problems then the next inspection
area is the connections of the system connectors. Most problems with the occurrence of system malfunction are from
conditions of vacuum line and connector connections and the causes from the malfunction of mechanical mechanism is
actually very few.
For example, when there are no problems with basic components, let's assume that there is a vehicle having vacuum
leak from connection slack in the vacuum line between EGR vacuum modulator and EGR valve. This vehicle, due to the
driving condition or, according to the circumstances, smog or other conditions, could create customer's complaint and
by connecting the scanning device could display as the malfunction of the EGR valve's potentiometer.
As previously explained, this car has a separate controller to control the Hoover EGR and, in accordance with various
input element, the controller controls EGR valve by regulating the force of vacuum being applied to the EGR valve through
PWM control. At this time, the controller has to receive feedback whether the EGR valve operates correctly according to
the value sent to the EGR modulator and this role is performed by the EGR potentiometer located at top section of the
EGR valve.
In other word, the controller sent correct output value to the EGR vacuum modulator but, due to the leakage of vacuum,
signal of required value can not be received from the EGR potentiometer causing to display as malfunction of related
parts.
As a reference, the EGR valve of diesel vehicle (DI Engine) controlling from the engine ECU to EGR system has different
shape than the Hoover EGR valve because the EGR valve's operation signal in the DI engine is performed by the HFM
sensor instead of the EGR potentiometer.
This principle is that when the EGR valve opens up to flow exhaust gas into the intake unit the amount of fresh air,
comparatively, will be reduced. The DI engine ECU receives feedback signal of change in amount of air being passed
through the HFM sensor according to the opening amount of the EGR valve.
Hoover EGR System for IDI Engine EGR System for DI Engine
(Including the EGR Valve Potentiometer)
Y220_04013
EXHAUST SYSTEM
CHANGED BY
EFFECTIVE DATE DI ENG SM - 2004.4
AFFECTED VIN