2006 MERCEDES-BENZ SPRINTER sensor

N2 and N3 Speed Sensors
The N2 and N3 Input Speed Sensors are two Hall-
effect speed sensors that are mounted internally in
the transmission and are used by the TCM to calcu-
late the transmission's input speed. Since the input
speed cannot be measured directly, two of the drive
elements are measured. Two input speed sensors
were required because both drive elements are not
active in all gears.
CAN C Bus Indirect Input Signals
A 2.5-volt bias (operating voltage) is present on the
CAN C bus any time the ignition switch is in the
RUN position. Both the TCM and the ABS apply this
bias. On this vehicle, the CAN C bus is used for mod-
ule data exchange only. The indirect inputs used on
the NAG1 electronic control system are:
²Wheel Speed Sensors.
²Brake Switch.
²Engine RPM.
²Engine Temperature.
²Cruise Control Status.
²Gear Limit Request.
²Throttle Position - 0% at idle, 100% at WOT. If
open, TCM assumes idle (0% throttle opening).
²Odometer Mileage
²Maximum Effective Torque.
²Engine in Limp-In Mode/Mileage Where DTC
Was Set.
BRAKE TRANSMISSION SHIFT INTERLOCK (BTSI)
The BTSI solenoid prevents shifting out of the
PARK position until the ignition key is in the RUN
position and the brake pedal is pressed. The TCM
controls the ground while the ignition switch supplies
power to the BTSI solenoid. The PCM monitors the
brake switch and broadcasts brake switch status
messages over the CAN C bus. If the park brake is
depressed and there is power (Run/Start) to SLA, the
BTSI solenoid deactivates.
SHIFT SCHEDULES
The basic shift schedule includes up and down-
shifts for all five gears. The TCM adapts the shift
program according to driving style, accelerator pedal
position and deviation of vehicle speed. Influencing
factors are:
²Road Conditions.
²Incline, Decline and Altitude.
²Trailer Operation, Loading.
²Engine Coolant Temperature.
²Cruise Control Operation.
²Sporty Driving Style.
²Low and High ATF Temperature.
Upshift
To :1-2 2-3 3-4 4-5
Activat-
ed By
Sole-
noid:1-2/4-5 2-3 3-4 1-2/4-5
Shift
Point
(at
35.2%
of throt-
tle)17.8
km/h
(11.6
mph)32.1
km/h
(19.95
mph)67.5
km/h
(41.94
mph)73.8
km/h
(45.86
mph)
Down-
shift
From:5-4 4-3 3-2 2-1
Activat-
ed By
Sole-
noid:1-2/4-5 3-4 2-3 1-2/4-5
Shift
Point55.7
km/h
(34.61
mph)40.5
km/h
(25.17
mph)24.4
km/h
(15.16
mph)15.1
km/h
(9.38
mph)
DOWNSHIFT SAFETY
Selector lever downshifts are not performed if inad-
missible high engine rpm is sensed.
ADAPTATION
To equalize tolerances and wear, an automatic
adaptation takes place for:
²Shift Time.
²Clutch Filling Time.
²Clutch Filling Pressure.
²Torque Converter Lock-Up Control.
Adaptation data may be stored permanently and to
some extent, can be diagnosed.
Driving Style Adaptation
The shift point is modified in steps based on the
information from the inputs. The control module
looks at inputs such as:
²vehicle acceleration and deceleration (calculated
by the TCM).
²rate of change as well as the position of the
throttle pedal (fuel injection information from the
ECM).
²lateral acceleration (calculated by the TCM).
²gear change frequency (how often the shift
occurs).
Based on how aggressive the driver is, the TCM
moves up the shift so that the present gear is held a
8E - 8 ELECTRONIC CONTROL MODULESVA

little longer before the next upshift. If the driving
style is still aggressive, the shift point is modified up
to ten steps. If the driving returns to normal, then
the shift point modification also returns to the base
position.
This adaptation has no memory. The adaptation to
driving style is nothing more than a shift point mod-
ification meant to assist an aggressive driver. The
shift points are adjusted for the moment and return
to base position as soon as the inputs are controlled
in a more rational manner.
Shift Time Adaptation (Shift Overlap Adaptation, Working
Pressure)
Shift time adaptation is the ability of the TCM to
electronically alter the time it takes to go from one
gear to another. Shift time is defined as the time it
takes to disengage one shift member while another is
being applied. Shift time adaptation is divided into
four categories:
1. Accelerating upshift, which is an upshift under
a load. For shift time adaptation for the 1-2 upshift
to take place, the transmission must shift from 1st to
2nd in six different engine load ranges vs. transmis-
sion output speed ranges.
2. Decelerating upshift, which is an upshift under
no load. This shift is a rolling upshift and is accom-
plished by letting the vehicle roll into the next gear.
3. Accelerating downshift, which is a downshift
under load. This shift can be initiated by the throttle,
with or without kickdown. The shift selector can also
be used.
4. Decelerating downshift, which is accomplished
by coasting down. As the speed of the vehicle
decreases, the transmission downshifts.
Fill Pressure Adaptation (Apply Pressure Adaptation, Modu-
lating Pressure)
Fill pressure adaptation is the ability of the TCM
to modify the pressure used to engage a shift mem-
ber. The value of this pressure determines how firm
the shift will be.
²If too much pressure is used, the shift will be
hard.
²If too little pressure is used, the transmission
may slip.
The pressure adjustment is needed to compensate
for the tolerances of the shift pressure solenoid valve.
The amount the solenoid valve opens as well as how
quickly the valve can move, has an effect on the pres-
sure. The return spring for the shift member pro-
vides a resistance that must be overcome by the
pressure in order for shift member to apply. These
return springs have slightly different values. This
also affects the application pressure and is compen-
sated for by fill pressure adaptation.Fill Time Adaptation (Engagement Time Adaptation)
Fill time is the time it takes to fill the piston cav-
ity and take up any clearances for a friction element
(clutch or brake). Fill time adaptation is the ability of
the TCM to modify the time it takes to fill the shift
member by applying a preload pressure.
CONTROLLER MODES OF OPERATION
Permanent Limp - In Mode
When the TCM determines there is a non-recover-
able condition present that does not allow proper
transmission operation, it places the transmission in
permanent Limp-In Mode. When the condition occurs
the TCM turns off all solenoids as well as the sole-
noid supply output circuit. If this occurs while the
vehicle is moving, the transmission remains in the
current gear position until the ignition is turned off
or the shifter is placed in the ªPº position. When the
shifter has been placed in ªP,º the transmission only
allows 2nd gear operation. If this occurs while the
vehicle is not moving, the transmission only allows
operation in 2nd gear.
Temporary Limp - In Mode
This mode is the same as the permanent Limp-In
Mode except if the condition is no longer present, the
system resumes normal operation.
Under Voltage Limp - In Mode
When the TCM detects that system voltage has
dropped below 8.5 volts, it disables voltage-depen-
dant diagnostics and places the transmission in the
temporary Limp-In Mode. When the TCM senses
that the voltage has risen above 9.0 volts, normal
transmission operation is resumed.
Hardware Error Mode
When the TCM detects a major internal error, the
transmission is placed in the permanent Limp-In
Mode and ceases all communication over the CAN
bus. When the TCM has entered this mode normal
transmission operation does not resume until all
DTCs are cleared from the TCM.
Loss of Drive
If the TCM detects a situation that has resulted or
may result in a catastrophic engine or transmission
problem, the transmission is placed in the neutral
position. Improper Ratio, Input Sensor Overspeed or
Engine Overspeed DTCs cause the loss of drive.
Controlled Limp - in Mode
When a failure does not require the TCM to shut
down the solenoid supply, but the failure is severe
enough that the TCM places the transmission into a
VAELECTRONIC CONTROL MODULES 8E - 9

volt, clean and tighten the battery negative cable
eyelet terminal connection to the engine block.
Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery negative cable.
REMOVAL
(1) Turn the ignition switch to the Off position. Be
certain that all electrical accessories are turned off.
(2) Disconnect and isolate the remote battery neg-
ative cable terminal.
(3) One at a time, trace and disconnect the battery
cable retaining pushpins, fasteners and routing clips
until the cables are free from the vehicle.
(4) Feed the battery cable assembly out of the
vehicle.
INSTALLATION
(1) Position the battery cable in the vehicle.
(2) One at a time, install the battery cable retain-
ing pushpins, fasteners and routing clips until the
cable is installed exactly in the factory installed loca-
tion in the vehicle. Refer to the Wiring Diagram sec-
tion of the service manual for reference.
(3) Connect the battery negative cable terminal.
BATTERY TRAY
DESCRIPTION
The battery is mounted in a stamped steel battery
tray located in the left front corner of the engine
compartment. The battery tray is secured with bolts
to the left front wheelhouse inner steel panel. A hole
in the bottom of the battery tray is fitted with aformed drain tube. A second hole in the bottom of the
tray is fitted with a battery temperature sensor.
OPERATION
The battery tray provides a mounting location and
support for the vehicle battery. The battery tray sup-
port supports the battery tray and provides an
anchor point for the inboard battery hold down hard-
ware. The battery tray and the battery hold down
hardware combine to secure and stabilize the battery
in the engine compartment, which prevents battery
movement during vehicle operation. Unrestrained
battery movement during vehicle operation could
result in damage to the vehicle, the battery or both.
The battery tray drain tube directs spilled water or
electrolyte from a leaking battery to the ground
through another hole in the front extension of the
left front wheelhouse inner panel.
REMOVAL
(1) Remove the battery from the battery tray.
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
(2) Remove the battery temperature sensor from
the battery tray. (Refer to 8 - ELECTRICAL/CHARG-
ING/BATTERY TEMPERATURE SENSOR -
REMOVAL).
(3) Remove the bolts that secure the battery tray
to the battery tray support.
(4) Remove the battery tray from the vehicle.
INSTALLATION
(1) Clean and inspect the battery tray. (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM - CLEANING).
(2) Position the battery tray onto the battery tray
support.
(3) Install and tighten the bolts that secure the
battery tray to the battery tray support. Tighten the
screws to 11.8 N´m (105 in. lbs.).
(4) Install the battery temperature sensor onto the
battery tray. (Refer to 8 - ELECTRICAL/CHARGING/
BATTERY TEMPERATURE SENSOR - INSTALLA-
TION).
(5) Install the battery onto the battery tray. (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
INSTALLATION).
Fig. 12 Test Ground Circuit Resistance - Typical
1 - VOLTMETER
2 - BATTERY
3 - ENGINE GROUND
8F - 16 BATTERY SYSTEMVA

HEATED SEATS
TABLE OF CONTENTS
page page
HEATED SEATS
DESCRIPTION.........................10
OPERATION...........................10
DIAGNOSIS AND TESTING - HEATED SEATS . 11
DRIVER HEATED SEAT SWITCH
DESCRIPTION.........................11
OPERATION...........................11
DIAGNOSIS AND TESTING - DRIVER HEATED
SEAT SWITCH........................11
REMOVAL.............................11
INSTALLATION.........................12
HEATED SEAT ELEMENT
DESCRIPTION.........................12
OPERATION...........................12
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT...........................12
HEATED SEAT RELAY
DESCRIPTION.........................12OPERATION...........................13
DIAGNOSIS AND TESTING - HEATED SEAT
RELAY..............................13
REMOVAL.............................13
INSTALLATION.........................13
HEATED SEAT SENSOR
DESCRIPTION.........................13
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR............................13
PASSENGER HEATED SEAT SWITCH
DESCRIPTION.........................13
OPERATION...........................13
DIAGNOSIS AND TESTING - PASSENGER
HEATED SEAT SWITCH.................14
REMOVAL.............................14
INSTALLATION.........................14
HEATED SEATS
DESCRIPTION
Individually controlled, electrically heated front
seats are available factory-installed optional equip-
ment on this model. Vehicles with this option can be
visually identified by the two separate heated seat
switches mounted in the instrument panel. The
heated seat system allows the front seat driver and
passenger to select from two different levels of sup-
plemental electrical seat heating, or no seat heating
to suit their individual comfort requirements. The
heated seat system for this vehicle includes the fol-
lowing major components, which are described in fur-
ther detail later in this section:
²Heated Seat Elements- Four heated seat ele-
ments are used per vehicle, two for each front seat.
One heating element in the seat back and one in the
seat cushion. The heated seat sensor is integral to
the seat cushion heating element. The heated seat
elements are integral to the front seat and seat back
cushions. Refer to heated seat elements later in this
section for additional information.
²Heated Seat Relay- One heated seat relay is
used per vehicle. The relay is located in the fuse
block and is responsible for distributing the voltage
(B+) to the heated seat elements.
²Heated Seat Sensors- Two heated seat sen-
sors are used per vehicle, one for each front seat. The
heated seat sensors are integral to each of the heatedseat element assemblies. Refer to heated seat sensor
later in this section for additional information.
²Heated Seat Switches- Two heated seat
switches are used per vehicle, one for each front seat.
The switches are mounted in the instrument panel.
Refer to heated seat switches later in this section for
additional information.
Hard wired circuitry connects the heated seat sys-
tem components to each other through the electrical
system of the vehicle. Refer to Wiring for additional
information. The wiring information includes wiring
diagrams, proper wire and connector repair proce-
dures, further details on wire harness routing and
retention, as well as pin-out and location views for
the various wire harness connectors, splices and
grounds.
OPERATION
The heated seat system is designed to provide indi-
vidually controlled, supplemental heat to the seat
cushion and seat back surfaces of both front seats.
Because this system converts electrical current to
heat, the heated seat system can provide a measure
of warm comfort almost immediately upon entering a
cold vehicle, rather than having to wait for the
engine coolant to reach sufficient temperature to
deliver heat through the conventional heater system.
This system allows each front seat occupant to indi-
vidually select one of two comfort levels, Hi or Lo, or
to turn the heater for their seat off.
8G - 10 HEATED SEATSVA

The heated seat system components operate on
battery current received through a fuse in the Fuse
Block on a fused ignition switch output (run-acc) cir-
cuit so that the system will only operate when the
ignition switch is in the On or Accessory positions.
The heated seat system will be turned Off automati-
cally whenever the ignition switch is turned to any
position except On or Accessory. Also, the heated seat
system will not operate when the surface tempera-
ture of the seat cushion cover at either heated seat
sensor is above the designed temperature set points
of the system.DIAGNOSIS AND TESTING - HEATED SEATS
Refer toWiringfor the appropriate wiring infor-
mation. The wiring information includes wiring dia-
grams, proper wire and connector repair procedures,
further details on wire harness routing and reten-
tion, as well as pin-out and location views for the
various wire harness connectors, splices and grounds.
HEATED SEAT SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
NO HEATED SEAT SWITCH
ILLUMINATION WITH IGNI-
TION ON1. Faulty fuse. 1. Check heated seat fuse in Fuse Block. Re-
place fuse, if required.
2. Wiring faulty. 2. Check fused ignition switch output (run-acc)
circuit from heated seat switch connector to igni-
tion switch. Repair, if required.
3. Ground faulty. 3. Check for ground at heated seat switch con-
nector. Repair, if required.
4. Faulty switch. 4. Refer to Heated Seat Switch for the proper
switch diagnosis and testing procedures.
DRIVER HEATED SEAT
SWITCH
DESCRIPTION
The heated seat switches are located on the instru-
ment panel, in the accessory switch bezel. The two,
momentary rocker type switches provide a signal to
the Heated Seat Relay through separate hard wired
circuits. Each switch contains two light emitting
diodes (LED), one for each High and Low setting to
let the occupant know that the seat heater system is
on.
The heated seat switches and their LED's cannot
be repaired. If either switch is faulty or damaged the
entire switch must be replaced.
OPERATION
There are three modes that can be selected with
each of the heated seat switches: Off, Low, and High.
When the top of the switch rocker is depressed, the
low mode is selected and the low mode LED indicator
illuminates. Depressing the top of the switch rocker a
second time will turn the heated seat to Off. This
same process is repeated for High heat setting. The
heated seats will automatically return to the Off
mode anytime the vehicle ignition switch is turned
Off.Both switches provide separate hard wire inputs to
the Heated Seat Relay to indicate the selected mode.
The Heated Seat Relay responds to the heated seat
switch messages by controlling the output to the seat
heater elements of the selected seat.
DIAGNOSIS AND TESTING - DRIVER HEATED
SEAT SWITCH
For circuit description and diagrams, refer toWir-
ing.
(1) Inspect the Heated Seat Switches for apparent
damage or sticking/binding and replace if required.
Refer to Heated Seat Switch Removal and Installa-
tion in this section.
(2) Replace the heated seat switch with a known
good unit and retest the heated seat system.
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the gear selector bezel trim. Refer to
the Body section for the procedure.
(3) Remove the storage bin. Refer to the Body sec-
tion for the procedure.
(4) Remove the switch bezel retaining screw and
remove the switch bezel from the instrument panel.
Refer to the Body section for the procedure.
(5) Disconnect electrical connections.
VAHEATED SEATS 8G - 11

(6) Working from the underside of the switch, gen-
tly rock the switch back and forth out of its mounting
location in the switch bezel.
INSTALLATION
(1) Install the heated seat switch in its mounting
location in the switch bezel.
(2) Connect electrical connections.
(3) Position the switch bezel and install the retain-
ing screw. Refer to the Body section for the proce-
dure.
(4) Install the storage bin. Refer to the Body sec-
tion for the procedure.
(5) Install the gear selector bezel trim. Refer to the
Body section for the procedure.
(6) Connect the negative battery cable.
HEATED SEAT ELEMENT
DESCRIPTION
The heated seat system includes two seat heating
elements in each front seat, one for the seat cushion
(Fig. 1) and the other for the seat back. All models
use two resistor wire heating elements for each seat
that are connected in series with the Heated Seat
Relay. The temperature sensor is a Negative Temper-
ature Coefficient (NTC) thermistor. One temperature
sensor is used for each seat, and it is located in the
seat cushion heating element for all models.The seat heating elements are glued onto the seat
and seat back cushions. The heated seat elements
and the temperature sensor cannot be adjusted or
repaired and, if faulty or damaged a new seat assem-
bly must be installed.
OPERATION
The heated seat elements resist the flow of electri-
cal current. When battery current is passed through
the elements, the energy lost by the resistance of the
elements is released in the form of heat. The heated
seat temperature sensor is a NTC thermistor. When
the temperature of the seat cushion cover rises, the
resistance of the sensor decreases. The heated seat
relay uses this temperature sensor input to monitor
the temperature of the seat, and regulates the cur-
rent flow to the seat heating elements accordingly.
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT
For complete circuit diagrams, refer toWiring.
NOTE: When checking heated seat elements for
continuity, be certain to move the heating element
being checked. Moving the element, such as sitting
in the seat will eliminate the possibility of an inter-
mittent open in the element which would only be
evident if the element was in a certain position.
Failure to check the element in various positions
could result in an incomplete test.
(1) Disconnect and isolate the battery negative
cable. Disconnect the heated seat element wire har-
ness connector from under the seat cushion. Check
for continuity between the seat heater driver circuit
and ground. There should be continuity, less than 7
ohms. If OK, go to Step 2. If not OK, replace the seat
assembly.
(2) Check for continuity between the seat heater
B+ driver circuit cavity and the seat back frame.
There should benocontinuity. If OK, heating ele-
ment is OK at this time. If not OK, replace the seat
assembly.
HEATED SEAT RELAY
DESCRIPTION
The heated seat relay is an electromechanical
device that switches 12v battery current to the
heated seat elements when the relay control coil is
energized. The heated seat relay is located in the
Fuse Block, under the drivers seat. The heated seat
relay is a International Standards Organization
(ISO) relay. Relays conforming to the ISO specifica-
tions have common physical dimensions, current
capacities, terminal patterns, and terminal functions.
Fig. 1 Heated Seat Element - Typical
1 - Seat Back Wire Harness
2 - Heated Seat Wire Harness Connector
3 - Heated Seat Cushion Element
8G - 12 HEATED SEATSVA

The heated seat relay cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact. When the electromagnetic coil is de-ener-
gized, spring pressure returns the movable contact to
the normally closed position. The resistor or diode is
connected in parallel with the electromagnetic coil in
the relay, and helps to dissipate voltage spikes that
are produced when the coil is de-energized.
DIAGNOSIS AND TESTING - HEATED SEAT
RELAY
The heated seat relay is located in the Fuse Block,
under the drivers seat. Refer toWiringfor the loca-
tion of complete heated seat system wiring diagrams.
(1) Remove the heated seat relay from the fuse
block.
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 3. If not OK, replace the faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
4. If not OK, replace the faulty relay.
(4) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, check the relay supply circuits. If not
OK, replace the faulty relay.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) The heated seat relay is located in the fuse
block, under the drivers seat. Refer to wiring for
detailed location.
(3) Grasp the heated seat relay firmly and pull it
straight out from the fuse block. A slight rocking
motion will aid in removal.
INSTALLATION
(1) Grasp the heated seat relay firmly and push it
straight in the fuse block.
(2) Reconnect the battery negative cable.
HEATED SEAT SENSOR
DESCRIPTION
The heated seat temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor. One tem-
perature sensor is used for each seat. The sensor is
located in the seat cushion heating element for all
models.
The heated seat sensor cannot be adjusted or
repaired and if it is found to be faulty, the complete
heated seat element must be replaced.
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR
For complete circuit diagrams, refer toWiring.
NOTE: Any resistance values (ohmsV) given in the
following text are supplied using the automatic
range generated by a FLUKETautomotive meter. If
another type of measuring device is used the val-
ues generated may not be the same as the results
shown here, or may have to be converted to the
range used here.
(1) Backprobe the heated seat relay wire harness
connector, do not disconnect. Using an voltmeter,
check the voltage of the seat temperature sensor
input cavity of the heated seat relay wire harness
connector. The seat sensor input voltage should be
between 1.7 volts and 3.0 volts with the system ON.
If OK, sensor is OK at this time. If not OK, replace
the faulty seat cushion heating element and sensor
assembly.
PASSENGER HEATED SEAT
SWITCH
DESCRIPTION
The heated seat switches are located on the instru-
ment panel, in the accessory switch bezel. The two,
momentary rocker type switches provide a signal to
the Heated Seat Relay through separate hard wired
circuits. Each switch contains two light emitting
diodes (LED), one for each High and Low setting to
let the occupant know that the seat heater system is
on.
The heated seat switches and their LED's cannot
be repaired. If either switch is faulty or damaged the
entire switch must be replaced.
OPERATION
There are three modes that can be selected with
each of the heated seat switches: Off, Low, and High.
When the top of the switch rocker is depressed, the
low mode is selected and the low mode LED indicator
illuminates. Depressing the top of the switch rocker a
VAHEATED SEATS 8G - 13

IGNITION CONTROL
TABLE OF CONTENTS
page page
IGNITION CONTROL
OPERATION - GLOW PLUG................1
SPECIAL TOOLS........................1
GLOW PLUG
REMOVAL.............................1
INSTALLATION..........................1GLOW PLUG RELAY
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - GLOW PLUG
RELAYS..............................2
IGNITION CONTROL
OPERATION - GLOW PLUG
Pre - Glowing
With the key in the On position, the glow plug out-
put stage and the indicator lamp are actuated by the
ECM. The pre-heating time is calculated by the ECM
in line with the coolant temperature. The glow plug
output stage switches the current through the glow
plugs. The glow plug indicator lamp goes out after a
pre-glow period has elapsed. Component or cable fail-
ures in the pre-glow system are indicated by the glow
plug lamp and stored in the ECM.
Glow Output Stage
With the ignition key in the On position a signal is
transmitted from the ECM to the glow plug output
stager. If no data is exchanged with the ECM the
glow plug stage is terminated after two seconds. The
glow plug out put stage constantly signals the cur-
rent operating state (ON/OFF) and any system
faults. The following faults are recognized by the out
put stage and transmitted to the ECM:
²Open circuit in one or more of the glow plug
leads
²Short circuit in the glow plug circuit
²Out put stage fault or temperature related shut-
off
If a failure in the glow plug system occurs, the
glow plug indicator lamp will be illuminated only as
long as the fault is current. If the failure is no longer
present, the glow plug indicator lamp will be
switched off but a code will be stored in the ECM.
After Glow
Once the engine has started, the ECM determines
the after glow time depending on cooling tempera-
ture. During this time the glow plugs continue to be
actuated by the glow plug output stage. This results
in improved smooth running after a cold start and
improved warming up properties, elimination of blueexhaust after a cold start up and a more stable cold
starting speed.
If no signal is received from the coolant tempera-
ture sensor the signal from the oil sensor is used as a
substitute.
SPECIAL TOOLS
GLOW PLUG
REMOVAL
(1) Disconnect the negative battery cable.
(2) Remove the engine cover.
(3) Use special tool #9286 pliers to unplug the
glow plug wiring harness connector(s) at the glow
plug.
(4) Remove the glow plug(s) (Fig. 1).
INSTALLATION
(1) Screw glow plug(s) into cylinder head and
tighten to 12 N´m (115 lbs. in) (Fig. 1).
(2) Connect the glow plug wiring harness connec-
tor(s)
(3) Install the engine cover.
(4) Connect negative battery cable.
GLOW PLUG RELAY
DESCRIPTION
The glow plug relay supplies battery voltage to the
glow plug through a timed cycle that is related to
coolant temperature. The glow plug relay is located
under the battery. The purpose of a glow plug system
GLOW PLUG PLIERS
VAIGNITION CONTROL 8I - 1