in the engine exhaust. This is accomplished by allow-
ing a predetermined amount of hot exhaust gas to
recirculate and dilute the incoming fuel/air mixture.

A malfunctioning EGR system can cause engine

stumble, sags, or hesitation, rough idle, engine stall-
ing and poor driveability.

OPERATION

The system consists of:
• An EGR valve assembly. The valve is located on

the rear of the engine above the exhaust manfiold.

• An EGR solenoid.The EGR solenoid controls the

“on time” of the EGR valve.

• The ECM operates the EGR solenoid. The ECM

is located inside the vehicle under the instrument
panel.

• An EGR tube connects a passage in the EGR

valve to the rear of the exhaust manifold.

• The vacuum pump supplies vacuum for the EGR

solenoid and the EGR valve. This pump also supplies
vacuum for operation of the power brake booster and
the heating and air conditioning system. The pump is
located internally in the front of the engine block and
is driven by the crankshaft gear.

• Vacuum lines and hoses connect the various

components.

When the ECM supplies a variable ground signal

to the EGR solenoid, EGR system operation starts to
occur. The ECM will monitor and determine when to
supply and remove this variable ground signal. This
will depend on inputs from the engine coolant tem-
perature, throttle position and engine speed sensors.

When the variable ground signal is supplied to the

EGR solenoid, vacuum from the vacuum pump will
be allowed to pass through the EGR solenoid and on
to the EGR valve with a connecting hose.

Exhaust gas recirculation will begin in this order

when:

• The ECM determines that EGR system opera-

tion is necessary.

• The engine is running to operate the vacuum

pump.

• A variable ground signal is supplied to the EGR

solenoid.

• Variable vacuum passes through the EGR sole-

noid to the EGR valve.

• The inlet seat (poppet valve) at the bottom of

the EGR valve opens to dilute and recirculate
exhaust gas back into the intake manifold.

The EGR system will be shut down by the ECM

after 60 seconds of continuous engine idling to
improve idle quality.

EXHAUST GAS RECIRCULATION

25 - 3

VALVE

DESCRIPTION

The EGR system consists of (Fig. 1):
• EGR valve

• EGR tube

• Vacuum hoses

• EGR solenoid

OPERATION

The engines use Exhaust Gas Recirculation (EGR)

systems. The EGR system reduces oxides of nitrogen
(NOx) in engine exhaust and helps prevent detona-
tion (engine knock). Under normal operating condi-
tions, engine cylinder temperature can reach more
than 3000°F. Formation of NOx increases proportion-
ally with combustion temperature. To reduce the
emission of these oxides, the cylinder temperature
must be lowered. The system allows a predetermined
amount of hot exhaust gas to recirculate and dilute
the incoming air/fuel mixture. The diluted air/fuel
mixture reduces peak flame temperature during com-
bustion.

REMOVAL

(1) Remove engine cover (Refer to 9 - ENGINE -

REMOVAL).

(2) Remove front wiper unit (Refer to 8 - ELEC-

TRICAL/WIPERS/WASHERS/WIPER

MODULE

REMOVAL).

(3) Disconnect EGR valve vacuum line.
(4) Remove EGR pipe to EGR valve retaining bolts

(Fig. 1).

(5) Remove EGR valve retaining nuts (Fig. 1) and

EGR valve.

INSTALLATION

(1) Clean gasket mating surfaces.
(2) Install EGR valve (Fig. 1). Torque nuts to

32.4N·m.

(3) Connect EGR pipe to EGR valve (Fig. 1).

Torque bolts to 32.4N·m

(4) Install front wiper unit (Refer to 8 - ELECTRI-

CAL/WIPERS/WASHERS/WIPER

MODULE

INSTALLATION).

(5) Install engine cover (Refer to 9 - ENGINE -

INSTALLATION).

Fig. 1 EGR and TURBOCHARGER COMPONENTS

1 - HOSE CLAMP
2 - COOLANT HOSE
3 - EGR VALVE RETAINING NUT
4 - EGR VALVE
5 - EGR GASKET
6 - EGR VALVE RETAINING STUDS
7 - EGR TUBE
8 - EXHAUST PIPE RETAINING BOLT (2)
9 - TURBOCHARGER BRACKET
10 - BRACKET RETAINING NUT
11 - TURBOCHARGER DOWN PIPE STUD
12 - TURBOCHARGER DOWN PIPE
13 - DOWN PIPE RETAINING NUT
14 - DOWN PIPE GASKET

25 - 4

EXHAUST GAS RECIRCULATION

ON-BOARD DIAGNOSTICS

TABLE OF CONTENTS

page

ON-BOARD DIAGNOSTICS

DESCRIPTION - DIAGNOSTIC TROUBLE

CODES

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

ON-BOARD DIAGNOSTICS

DESCRIPTION - DIAGNOSTIC TROUBLE CODES

On the following pages, a list of DTC’s is provided

for the 2.5L diesel engine. A DTC indicates that the
ECM has recognized an abnormal signal in a circuit
or the system. A DTC may indicate the result of a
failure, but most likely will not identify the failed
component directly. Refer to the appropriate diagnos-
tic manual for more information on diagnosis of trou-
ble codes.

ACCESSING DIAGNOSTIC TROUBLE CODES

A stored DTC can be displayed through the use of

the DRB III

t scan tool. The DRB IIIt connects to the

data link connector. The data link connector is
located under the instrument panel near bottom of
the steering column

ERASING TROUBLE CODES

After the problem has been repaired, use the DRB

III

t scan tool to erase a DTC.

ENGINE CONTROL MODULE (ECM) - DRBIII

T CODES

Generic Scan Tool Code

DRB III

Scan Tool Display

P0070

Ambient Air Temperature Circuit Signal Voltage Too High

Ambient Air Temperature Circuit Signal Voltage Too Low

P0100

Mass Air Flow Sensor Plausibility

Mass Air Flow Sensor Plausibility Positive Area

Mass Air Flow Sensor Signal Voltage Too High

Mass Air Flow Sensor Signal Voltage Too Low

Mass Air Flow Sensor Supply Voltage Too High Or Low

P0105

Barometric Pressure Circuit Signal Voltage To High

Barometric Pressure Circuit Signal Voltage To Low

P0110

Intake Air Temperature Sensor Circuit Signal Too High

Intake Air Temperature Sensor Circuit Signal Too Low

P0115

Engine Coolant Temperature Sensor Circuit Engine Is Cold Too Long

Engine Coolant Temperature Sensor Circuit Voltage To Low

Engine Coolant Temperature Sensor Circuit Voltage To High

P0190

Fuel Pressure Sensor Circuit MALF Signal Voltage Too High

Fuel Pressure Sensor Circuit MALF Signal Voltage Too Low

P0195

Oil Temperature Sensor Circuit MALF Signal Voltage Too High

Oil Temperature Sensor Circuit MALF Signal Voltage Too Low

P0201

Cylinder 1 Injector Circuit Current Decrease

ON-BOARD DIAGNOSTICS

25 - 5

Generic Scan Tool Code

DRB III

Scan Tool Display

Cylinder 1 Injector Circuit Load Drop

Cylinder 1 Injector Circuit Overcurrent High Side

Cylinder 1 Injector Circuit Overcurrent Low Side

P0202

Cylinder 2 Injector Circuit Current Decrease

Cylinder 2 Injector Circuit Load Drop

Cylinder 2 Injector Circuit Overcurrent High Side

Cylinder 2 Injector Circuit Overcurrent Low Side

P0203

Cylinder 3 Injector Circuit Current Decrease

Cylinder 3 Injector Circuit Load Drop

Cylinder 3 Injector Circuit Overcurrent High Side

Cylinder 3 Injector Circuit Overcurrent Low Side

P0204

Cylinder 4 Injector Circuit Current Decrease

Cylinder 4 Injector Circuit Load Drop

Cylinder 4 Injector Circuit Overcurrent High Side

Cylinder 4 Injector Circuit Overcurrent Low Side

P0235

Boost Pressure Sensor Plausibility

Boost Pressure Sensor Signal Voltage Too Low

Boost Pressure Sensor Signal Voltage Too High

Boost Pressure Sensor Signal Voltage Too High Or Low

P0335

CKP Position Sensor Circuit Dynamic Plausibility

CKP Position Sensor Circuit Overspeed Recognition

CKP Position Sensor Circuit Static Plausibility

P0340

CMP Position Sensor Circuit CMP/CKP Sync. Failure

CMP Position Sensor Circuit Dynamic Plausibility

CMP Position Sensor Circuit Fuel Shut-Off Activated

CMP Position Sensor Circuit Signal Frequency Too High

CMP Position Sensor Circuit Static Plausibility

P0380

Glow Plug Circuit A Open Circuit

Glow Plug Circuit A Short Circuit

P0403

EGR Solenoid Circuit Open Circuit

EGR Solenoid Circuit Short Circuit

P0480

Fan 1 Control Circuit Open Circuit

Fan 1 Control Circuit Short Circuit

P0481

Fan 2 Control Circuit Open Circuit

Fan 2 Control Circuit Short Circuit

25 - 6

ON-BOARD DIAGNOSTICS

ON-BOARD DIAGNOSTICS (Continued)

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