Dodge dakota 2002 Service Manual page 401

8E - 20 ELECTRONIC CONTROL MODULES
TRANSMISSION CONTROL MODULE (Continued)
NOTE: If the TCM has been replaced, the "Quick Learn
Procedure" must be performed. (Refer to 8 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/TRANSMIS-
SION CONTROL MODULE - STANDARD PROCEDURE)
BATTERY FEED
A fused, direct battery feed to the TCM is used for
continuous power. This battery voltage is necessary
to retain memory in the TCM. When the battery (B+)
is disconnected, this memory is lost. When the bat-
tery (B+) is restored, this memory loss is detected by
the TCM and a Diagnostic Trouble Code (DTC) is set.
CLUTCH VOLUME INDEXES (CVI)
An important function of the TCM is to monitor
Clutch Volume Indexes (CVI). CVIs represent the vol-
ume of fluid needed to compress a clutch pack.
The TCM monitors gear ratio changes by monitor-
ing the Input and Output Speed Sensors. The Input,
or Turbine Speed Sensor sends an electrical signal to
the TCM that represents input shaft rpm. The Out-
put Speed Sensor provides the TCM with output
shaft speed information.
By comparing the two inputs, the TCM can deter-
mine transmission gear position. This is important to
the CVI calculation because the TCM determines
CVIs by monitoring how long it takes for a gear
change to occur (Fig. 11).
Gear ratios can be determined by using the
DRBIII Scan Tool and reading the Input/Output
Speed Sensor values in the "Monitors" display. Gear
ratio can be obtained by dividing the Input Speed
Sensor value by the Output Speed Sensor value.
For example, if the input shaft is rotating at 1000
rpm and the output shaft is rotating at 500 rpm,
then the TCM can determine that the gear ratio is
2:1. In direct drive (3rd gear), the gear ratio changes
to 1:1. The gear ratio changes as clutches are applied
and released. By monitoring the length of time it
takes for the gear ratio to change following a shift
request, the TCM can determine the volume of fluid
used to apply or release a friction element.
The volume of transmission fluid needed to apply
the friction elements are continuously updated for
adaptive controls. As friction material wears, the vol-
ume of fluid need to apply the element increases.
Certain mechanical problems within the input
clutch assembly can cause inadequate or out-of-range
element volumes. Also, defective Input/Output Speed
Sensors and wiring can cause these conditions. The
following chart identifies the appropriate clutch vol-
umes and when they are monitored/updated:
Fig. 11 Example of CVI Calculation
1 - OUTPUT SPEED SENSOR
2 - OUTPUT SHAFT
3 - CLUTCH PACK
4 - SEPARATOR PLATE
5 - FRICTION DISCS
6 - INPUT SHAFT
7 - INPUT SPEED SENSOR
8 - PISTON AND SEAL
CLUTCH VOLUMES
Clutch When Updated
2-1 or 3-1
L/R
3-2 kickdown
2C
OD 2-3 upshift
4C 3-4 upshift
4-3 kickdown
UD
SHIFT SCHEDULES
As mentioned earlier, the TCM has programming that
allows it to select a variety of shift schedules. Shift
schedule selection is dependent on the following:
• Shift lever position
• Throttle position
• Engine load
• Fluid temperature
• Software level
As driving conditions change, the TCM appropri-
ately adjusts the shift schedule. Refer to the follow-
ing chart to determine the appropriate operation
expected, depending on driving conditions.
Proper Clutch
Volume
45 to 134
downshift
25 to 85
shift
30 to 100
30 to 85
30 to 100
shift
DR