Mitsubishi Outlander XL. Manual - part 1261

EXHAUST GAS RECIRCULATION (EGR) VALVE

ZK604041

Outlet

Coil

Magnet

Rotor

Shaft

Valve

Inlet

AA00

An EGR valve is installed in the inlet manifold plenum.The EGR
valve controls EGR flow volume using the stepper motor method
and reduces exhaust gas (NOx) and fuel consumption. The EGR
valve drives the stepper motor based on the signal from ECM.
When stepper motor rotor turns in clockwise or anti-clockwise
direction, the shaft fitted with a rotor and a screw expands and
contracts and the movement of the shaft causes the valve to go
up and down. Thus, EGR path gap is controlled minutely. The
stepper  motor  turns  15°  per  step.  The  stepper  motor  turns
forward or back only up to the angle dictated by the number of
pulse signals (number of steps) from the ECM. In other words,
increase and decrease of the EGR flow volume depends on the
number of signals (number of steps) from ECM. ECM changes
current flow to the 4 coils (A, B, C, D) in the stepper motor in
sequence according to the phase pattern in the following chart
in  order  to  turn  the  stepper  motor  rotor.  Open  valve  changes
phase in order of 0 → 1 → 2 → 3 → 0. Close valve changes
phase in order of 3 → 2 → 1 → 0 → 3.

Phase
number

Stepper motor coil
Coil A

Coil B

Coil C

Coil D

0

ON

OFF

OFF

ON

1

ON

OFF

ON

OFF

2

OFF

ON

ON

OFF

3

OFF

ON

OFF

ON

17c-8

EMISSION CONTROL

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

ZK602525

EGR
(stepper motor)

Coil

A

Coil

B

Coil

D

Coil

C

AA00

From MFI relay

Flow rate

Step

ECM

EMISSION REDUCTION SYSTEMS

M21701000005USA0000010000

These  decrease  CO,  HC  and  NOx  in  the  exhaust
gases  and  consist  of  air-fuel  ratio  feedback  control
and catalytic converter.

1. AIR-FUEL RATIO FEEDBACK CONTROL

Refer to GROUP 13A - Fuel Injection Control P.13A-31.

2. CATALYTIC CONVERTER

ZK602526 AA00

Catalytic converter

Catalytic converter is installed in the exhaust manifold junction
of each bank and in the center of exhaust pipe below the floor.
Based  on  appropriate  air-fuel  ratio  feedback  from  oxygen
sensor, CO and HC are oxidized and NOx is reduced. Catalytic
converter is a monolith with beehive design with catalysts on the
unit  surface.  It  is  protected  by  a  thermally  insulating  mat  and
enclosed in a shell.

EMISSION CONTROL

17c-9

EMISSION REDUCTION SYSTEMS

3. HC TRAP CATALYTIC CONVERTER

<California>

ZK602531AA00

Three-way catalyst

Exhaust
gas

HC trap catalyst

The  HC  trap  catalytic  converter  is  installed  to  the  center  of
exhaust  pipe  under  the  vehicle's  floor.  The  HC  trap  catalytic
converter  consists  of  the  HC  trap  catalyst  and  the  three-way
catalysts, which are the monolith type; the catalyst element is
attached  to  the  honeycomb  catalyst  surface.  The  HC  trap
catalyst  and  the  three-way  catalysts  are  held  by  the  heat-
insulating mat and installed in the shell. The HC trap catalyst
temporarily absorbs the exhaust HC from the engine within the
temperature  range  in  which  the  three-way  catalyst  is  not
activated, and prevents the exhaust HC from releasing outside
the vehicle. After that, the HC trap catalyst temperature rises and
releases the absorbed HC. The released HC is burnt out in the
downstream three-way catalyst.

CENTER EXHAUST PIPE HEATED OXYGEN

SENSOR

ZK603449AA00

Center exhaust pipe
heated oxygen sensor

HC trap catalytic
converter

The center exhaust pipe heated oxygen sensor is installed to the
HC  trap  catalytic  converter.  The  center  exhaust  pipe  heated
oxygen sensor detects the oxygen density of the exhaust gas
and  outputs  the  voltage  to  the  ECM  in  accordance  with  the
oxygen density.
The ECM uses this output voltage to detect the deterioration of
the  HC  trap  catalytic  converter.  The  structure  of  the  center
exhaust pipe heated oxygen sensor is the same as that of the
heated oxygen sensor (rear) installed in the exhaust manifold on
the both banks.

17c-10

EMISSION CONTROL

EMISSION REDUCTION SYSTEMS

HC TRAP CATALYTIC CONVERTER

DETERIORATION MONITOR

ZK602532

 ECM

Oxygen sensor (rear)

Center exhaust
pipe heated
oxygen sensor

HC trap catalyst converter

Engine coolant
temperature sensor

Accelerator pedal
position sensor

Crankshaft position sensor

AA00

The  ECM  detects  the  deterioration  of  the  HC  trap  catalytic
converter.
When  reaching  the  certain  operating  range,  the  ECM  begins
monitoring  the  difference  in  the  feedback  time  between  the
heated  oxygen  sensor  (rear)  on  the  upstream  of  the  HC  trap
catalyst and the center exhaust pipe heated oxygen sensor on
the downstream of the HC trap catalyst. This monitoring allows
the  ECM  to  detect  the  deterioration  of  the  HC  trap  catalytic
converter.

EMISSION CONTROL

17c-11

EMISSION REDUCTION SYSTEMS