Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 206
• Position of selector lever.
• Selected shift range.
• CAN signals.
• Engine Status.
Engine speed limits may be reached in all gears
with full throttle or in kick-down operation. In for-
ward driving, the shift range of the forward gears
can be adjusted by the operator by tipping the selec-
tor lever to the left or right (AutoStick). However, the
TCM features a downshift inhibitor to prevent the
engine from overspeeding.
OPERATION
The transmission control module (TCM) deter-
mines the current operating conditions of the vehicle
and controls the shifting process for shift comfort and
driving situations. It receives this operating data
from sensors and broadcast messages from other
modules.
The TCM uses inputs from several sensors that are
directly hardwired to the controller and it uses sev-
eral indirect inputs that are used to control shifts.
This information is used to actuate the proper sole-
noids in the valve body to achieve the desired gear.
The shift lever assembly (SLA) has several items
that are monitored by the TCM to calculate shift
lever position. The reverse light switch, an integral
part of the SLA, controls the reverse light relay con-
trol circuit. The Brake/Transmission Shift Interlock
(BTSI) solenoid and the park lockout solenoid (also
part of the SLA) are controlled by the TCM.
The ECM and ABS broadcast messages over the
controller area network (CAN C) bus for use by the
TCM. The TCM uses this information, with other
inputs, to determine the transmission operating con-
ditions.
The TCM:
• determines the momentary operating conditions
of the vehicle.
• controls all shift processes.
• considers shift comfort and the driving situation.
The TCM controls the solenoid valves for modulat-
ing shift pressures and gear changes. Relative to the
torque being transmitted, the required pressures are
calculated from load conditions, engine rpm, vehicle
speed, and ATF temperature.
The following functions are contained in the TCM:
• Shift Program
• Downshift Safety
• Torque Converter Lock-Up Clutch.
• Adaptation.
This transmission does not have a TCM relay.
Power is supplied to the SLA and the TCM directly
from the ignition.
The TCM continuously checks for electrical prob-
lems, mechanical problems, and some hydraulic prob-
lems. When a problem is sensed, the TCM stores a
diagnostic trouble code (DTC). Some of these codes
cause the transmission to go into “Limp-In” or
“default”
mode.
Some
DTCs
cause
permanent
Limp-In and others cause temporary Limp-In. The
NAG1 defaults in the current gear position if a DTC
is detected, then after a key cycle the transmission
will go into Limp-in, which is mechanical 2nd gear.
Some DTCs may allow the transmission to resume
normal operation (recover) if the detected problem
goes away. A permanent Limp-In DTC will recover
when the key is cycled, but if the same DTC is
detected for three key cycles the system will not
recover and the DTC must be cleared from the TCM
with the DRBIII
t scan tool.
TCM SIGNALS
The TCM registers one part of the input signals by
direct inputs, the other part by CAN C bus. In addi-
tion to the direct control of the actuators, the TCM
sends various output signals by CAN C bus to other
control modules.
Selector Lever Position
The TCM monitors the SLA for all shift lever posi-
tions via the CAN bus.
ATF Temperature Sensor
The ATF temperature sensor is a positive temper-
ature co-efficient (PTC) thermistor. It measures the
temperature of the transmission fluid and is a direct
input signal for the TCM. The temperature of the
ATF has an influence on the shifttime and resulting
shift quality. As the temperature rises, resistance
rises, and therefore, the probing voltage is decreas-
ing. Because of its registration, the shifting process
can be optimized in all temperature ranges.
The ATF temperature sensor is wired in series
with the park/neutral contact. The temperature sig-
nal is transmitted to the TCM only when the reed
contact of the park/neutral contact is closed because
the TCM only reads ATF temperature while in any
forward gear, or REVERSE. When the transmission
is in PARK or NEUTRAL, the TCM will substitute
the engine temperature for the ATF temperature.
Starter Interlock
The TCM monitors a contact switch wired in series
with the transmission temperature sensor to deter-
mine PARK and NEUTRAL positions. The contact
switch is open in PARK and NEUTRAL. The TCM
senses transmission temperature as high (switch
supply voltage), confirming switch status as open.
The TCM then broadcasts a message over CAN bus
to confirm switch status. The PCM receives this
information and allows operation of the starter cir-
cuit.
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ELECTRONIC CONTROL MODULES
8E - 7
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:
• Wheel Speed Sensors.
• Brake Switch.
• Engine RPM.
• Engine Temperature.
• Cruise Control Status.
• Gear Limit Request.
• Throttle Position - 0% at idle, 100% at WOT. If
open, TCM assumes idle (0% throttle opening).
• Odometer Mileage
• Maximum Effective Torque.
• Engine 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:
• Road Conditions.
• Incline, Decline and Altitude.
• Trailer Operation, Loading.
• Engine Coolant Temperature.
• Cruise Control Operation.
• Sporty Driving Style.
• Low 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
Point
55.7
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:
• Shift Time.
• Clutch Filling Time.
• Clutch Filling Pressure.
• Torque 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:
• vehicle acceleration and deceleration (calculated
by the TCM).
• rate of change as well as the position of the
throttle pedal (fuel injection information from the
ECM).
• lateral acceleration (calculated by the TCM).
• gear 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 MODULES
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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.
• If too much pressure is used, the shift will be
hard.
• If 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 “P” position. When the
shifter has been placed in “P,” 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
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ELECTRONIC CONTROL MODULES
8E - 9
predefined gear, there are several shift performance
concerns. For instance, if the transmission is slip-
ping, the controller tries to place the transmission
into 3rd gear and maintain 3rd gear for all forward
drive conditions.
STANDARD PROCEDURE - TCM ADAPTATION
The adaptation procedure requires the use of the
appropriate scan tool. This program allows the elec-
tronic transmission system to re-calibrate itself. This
will provide the proper baseline transmission opera-
tion. The adaptation procedure should be performed
if any of the following procedures are performed:
• Transmission Assembly Replacement
• Transmission Control Module Replacement
• Clutch Plate and/or Seal Replacement
• Electrohydraulic Unit Replacement or Recondi-
tion
(1) With the scan tool, reset the Transmission
adaptives. Resetting the adaptives will set the adap-
tives to factory settings.
NOTE: Perform the Coast Down Adaptations first.
The Transmission Temperature must be greater
than 60°C (140°F) and less than 70°C (158°F). Fail-
ure to stay within these temperature ranges will
void the procedure.
(2) Drive the vehicle until the transmission tem-
perature is in the specified range.
(3) Perform 4 to 5 coast downs from 5th to 4th
gear and then 4th to 3rd gear.
NOTE: For Upshift adaptation, the Transmission
temperature must be greater than 60°C (140°F) and
less than 100°C (212°F). Failure to stay within these
temperature ranges will void this procedure.
(4) From a stop, moderately accelerate the vehicle
and obtain all forward gear ranges while keeping the
Engine RPM below 1800 RPM. Repeat this procedure
4 to 5 times.
(5) Obtaining 5th gear may be difficult at 1800
RPM. Allow the transmission to shift into 5th gear at
a higher RPM then lower the RPM to 1800 and per-
form manual shifts between 4th and 5th gears using
the shift lever.
(6) The TCM will store the adaptives every 10
minutes. After completion of the adaptation proce-
dure make sure the vehicle stays running for at least
10 minutes.
(7) It is possible to manually store the adaptives
under the 10 minute time frame using the DRBIII
t
Store Adaptives procedure.
8E - 10
ELECTRONIC CONTROL MODULES
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