Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 529

VALVE

DESCRIPTION

Exhaust gas recirculation reduces the quantity of

fresh air supplied to the cylinders per stroke without
having to throttle the air supply. Exhaust gas is
recirculated during all engine speed and engine load
conditions. As a result, emissions are reduced. If a
quantity of exhaust gas is mixed with the air that is
to be used to burn the fuel in the cylinders, the oxy-
gen content is reduced because the exhaust gas is
low in oxygen. The result is that the combustion rate
is reduced, as is the combustion temperature. This
reduces the quantity of NOx that are emitted in the
exhaust gas. (Fig. 2).

The ECM power supply relay has a power off delay

feature. The relay is powered off approximately 15
seconds after the ignition switch is turned off. This
allows for the self-cleaning function of the EGR valve
and a function check of the sensors for diagnosis pur-
poses.

Fig. 1 EGR AND COOLER

1 - EGR VALVE

3 - COOLING FINS

2 - COOLANT PASSAGE

4 - EXHAUST GAS PASSAGE

VA

EXHAUST GAS RECIRCULATION

25 - 5

OPERATION

The mass of the air supplied to the cylinders per

stroke is the decisive factor for determining the opti-
mum quantity of exhaust gas for the operating con-
dition. This is calculated from the Mass Air Flow
sensor information.

The ECM evaluates this signal as well as that

from the Charge Air Pressure sensor, and outputs a
PWM signal in accordance with one of the maps
stored in it. The signal is sent to the exhaust gas
recirculation valve. The map is formulated to keep
the NOx as low as possible. The EGR valve is actu-
ated by an electric positioning motor and has a self
cleaning function. Every time the ignition switch is
turned off, the valve rotates twice to eliminate any
carbon deposits.

REMOVAL

NOTE: The EGR and EGR Cooler are serviced as an
assembly.

(1) Disconnect the negative battery cable.
(2) Partailly drain the cooling system (Refer to 7 -

COOLING/ENGINE/COOLANT - STANDARD PRO-
CEDURE).

(3) Lift up on the charge air hose retaining clip at

the intake manifold and disconnect hose with seal

(4) Disconnect the electrical connector at the EGR

positioner (Fig. 3).

(5) Disconnect the EGR cooler hose.
(6) Remove the EGR fasteners and EGR with

cooler assembly (Fig. 3).

INSTALLATION

(1) Clean all gasket mating surfaces.
(2) Position the EGR positioner to the intake man-

ifold with a new gasket, install bolts and tighten to
124 lbs.in (14 N·m) (Fig. 3).

(3) Connect the EGR positioner electrical connec-

tor (Fig. 3).

(4) Inspect the seal of the charge air inlet tube,

replace as necessary (Fig. 3).

(5) Seat the charge air tube with gasket into the

intake manifold and push down on the charge air
tube retaining clip.

(6) Refill the cooling system (Refer to 7 - COOL-

ING/ENGINE/COOLANT

-

STANDARD

PROCE-

DURE).

(7) Connect negative battery cable.

VALVE COOLER

DESCRIPTION

The exhaust gas recirculation (EGR) cooler is an

integrated part of the EGR valve. Coolant flows
around the exhaust gasses, cooling them before they
are remixed with the incoming air and reburned in
the combustion chamber (Fig. 4).

Fig. 2 EXHAUST GAS RECIRCULATION

1 - EGR VALVE
2 -CHARGE AIR PRESSURE SENSOR
3 - EXHAUST MANIFOLD
4 - EGR DUCT IN CYLINDER HEAD
5 - INTAKE MANIFOLD

Fig. 3 EGR VALVE

1 - EGR VALVE
2 - INTAKE MANIFOLD
3 - EGR COOLER HOSE
4 - HARNESS CONNECTOR

25 - 6

EXHAUST GAS RECIRCULATION

VA

The EGR valve and Cooler are serviced as an

assembly, refer to (Refer to 25 - EMISSIONS CON-
TROL/EXHAUST GAS RECIRCULATION/VALVE -
REMOVAL).

Fig. 4 EGR AND COOLER

1 - EGR VALVE
2 - EGR COOLER
3 - INTAKE MANIFOLD

VA

EXHAUST GAS RECIRCULATION

25 - 7

1.0

INTRODUCTION

The procedures contained in this manual include

all of the specifications, instructions, and graphics
needed to diagnose NAG1 Electronic Automatic
Transmission and Shift Lever Assembly problems.
The diagnostics in this manual are based on the
failure condition or symptom being present at the
time of diagnosis.

When repairs are required, refer to the appropri-

ate volume of the service information for the proper
removal and repair procedure.

READ THIS MANUAL BEFORE TRYING TO
DIAGNOSE A VEHICLE TROUBLE CODE.

Diagnostic procedures change every year. New

diagnostic systems may be added and/or carryover
systems may be enhanced. It is recommended that
you review the entire manual to become familiar
with all new and changed diagnostic procedures.

1.1

SYSTEM COVERAGE

This diagnostic procedures manual covers all

Sprinter (VA) equipped with a NAG1 Automatic
Transmission.

1.2

SIX -STEP TROUBLESHOOTING
PROCEDURE

Diagnosis of the NAG1 electronic transmission is
done in six basic steps:

Verification of complaint
Verification of any related symptoms
Symptom analysis
Problem isolation
Repair of isolated problem
Verification of proper operation

2.0

IDENTIFICATION OF
SYSTEM

The NAG1 Transmission family can be identified

by the presence of a 13 pin electrical connector, with
a bayonet lock on the right hand side of the trans-
mission. The connector is oriented horizontally.

3.0

SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION

3.1

GENERAL DESCRIPTION

The NAG1 electronic transmission is an electron-

ically controlled five speed transmission with a
controlled slip torque converter. The NAG1 elec-

tronic transmission is a conventional transmission
in that it uses hydraulically applied clutches to shift
a planetary gear train. However, the electronic
control system replaces many of the mechanical and
hydraulic components used in conventional trans-
mission valve bodies.

The ratios for the gear stages are obtained by 3

planetary gear sets. Fifth Gear is designed as an
Overdrive with a high speed ratio. The gears are
actuated electronically/hydraulically. The electronic
control system enables precise adaptation of pres-
sures to the respective operating conditions and to
the engine output during a shift phase, which
results in a significant improvement in shift qual-
ity.

3.2

FUNCTIONAL OPERATION

The NAG1 electronic transmission has a fully

adaptive control system. The system performs its
functions based on continuous real-time sensor and
switch feedback information. In addition the TCM
receives information from the Shift Lever Assembly,
ECM (engine management) and ABS (chassis sys-
tems) controllers over the CAN bus. The CAN bus is
a high speed communication bus that allows real
time control capability between various controllers.
Most messages are sent every 20 milliseconds, this
means critical information can be shared between
the Transmission, Shifter, Engine and ABS control-
lers. The CAN bus is a two wire bus with a CAN C
Bus (+) circuit and a CAN C Bus (-) circuit. The
CAN bus uses a twisted pair of wires in the harness
to reduce the potential of radio and noise interfer-
ence. The CAN bus also uses a 120 ohm terminating
resistor in both the ECM and Sentry Key Remote
Entry Module (SKREEM) modules. The module
terminating resistance is measured across both
CAN bus circuits at the ECM or SKREEM module.

The control system automatically adapts to

changes in engine performance, vehicle speed, and
transmission temperature variations to provide
consistent shift quality. The control system ensures
that clutch operation during upshifting and down-
shifting is more responsive without increased
harshness. The TCM controls the actuation of sole-
noid valves for modulating shift pressure and gear
change. The required pressure level is calculated
from the load condition, engine speed. Power for the
transmission system is supplied through the Trans-
mission Relay. The TCM is located in the under the
drivers seat of the vehicle.

The Transmission Control Module (TCM) contin-

uously checks for electrical problems, mechanical
problems, and some hydraulic problems. When a
problem is sensed, the TCM stores a diagnostic
trouble code (DTC). Some of these codes cause the
transmission to go into

9limp-in9 or 9default9 mode.

1

GENERAL INFORMATION