Table of Contents
Advertisement
8E - 8
ELECTRONIC CONTROL MODULES
POWERTRAIN CONTROL MODULE (Continued)
TRANSMISSION CONTROL (2.4L MODELS ONLY)
CVI CALCULATION
An important function of the PCM is to monitor
Clutch Volume Index (CVI). CVIs represent the vol-
ume of fluid needed to compress a clutch pack.
The PCM 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 PCM that represents input shaft rpm. The Out-
put Speed Sensor provides the PCM with output
shaft speed information.
By comparing the two inputs, the PCM can deter-
mine transaxle gear ratio. This is important to the
CVI calculation because the PCM determines CVIs
by monitoring how long it takes for a gear change to
occur (Fig. 5).
Gear ratios can be determined by using the DRB
Scan Tool and reading the Input/Output Speed Sen-
sor 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 PCM 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 PCM 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.
Clutch
L/R
2/4
OD
UD
SHIFT SCHEDULES
The PCM 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
CLUTCH VOLUMES
Shift Sequence
Oil Temperature
2-1 or 3-1 coast
downshift
1-2 shift
2-3 shift
4-3 or 4-2 shift
Fig. 5 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
Certain mechanical problems within the clutch
assemblies (broken return springs, out of position
snap rings, excessive clutch pack clearance, improper
assembly, etc.) can cause inadequate or out-of-range
clutch 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:
When Updated
> 70°
> 110°
• Software level
As driving conditions change, the PCM appropri-
ately adjusts the shift schedule. Refer to the follow-
ing chart to determine the appropriate operation
expected, depending on driving conditions.
Throttle Angle
< 5°
5 - 54°
> 5°
JR
Proper Clutch
Volume
35 to 83
20 to 77
48 to 150
24 to 70
Advertisement
Table of Contents
