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