Road Test
Note: The Road Test Procedure
should be performed only as part of the Symptom Diagnosis. Refer to
Symptoms - Automatic Transmission .
The following test provides a method of evaluating the condition
of the automatic transmission. The test is structured so that most
driving conditions would be achieved. The test is divided into the
following parts:
• |
Electrical Function Check |
• |
Upshift Control and Torque Converter
Clutch (TCC) Apply |
• |
Part Throttle Step-In Downshifts |
• |
Manual Gear Range Selection |
Note: Complete the test in the
sequence given. Incomplete testing cannot guarantee an accurate
evaluation.
Before the road test, ensure the following:
• |
The engine is performing properly. |
• |
Tire pressure is correct. |
During the road test:
• |
Perform the test only when traffic conditions
permit. |
• |
Operate the vehicle in a controlled, safe
manner. |
• |
Observe all traffic regulations. |
• |
View the scan tool data while conducting this
test. |
|
Take along qualified help in order to operate the
vehicle safely. |
• |
Observe any unusual sounds or smells. |
After the road test, check the following:
• |
Inspect for any diagnostic trouble
codes (DTCs) that may have set during the testing. Refer to
the applicable DTC. |
• |
Monitor the scan tool data for any abnormal
readings or data. |
Electrical Function Check
Perform this procedure first in order to ensure the electronic
transmission components are functioning properly. If these
components are not checked, a simple electrical condition could be
misdiagnosed.
- Connect the scan tool.
- Ensure the gear selector is in PARK and set the
parking brake.
- Start the engine.
- Verify that the following scan tool data can be
obtained and is functioning properly.
Refer to
Control Module References for typical data values. Data that is
questionable may indicate a concern.
• |
Line PC Sol. Pressure Cmd. |
• |
Calc. Throttle Position |
• |
PC Sol. 2 Pressure Cmd. |
• |
PC Sol. 3 Pressure Cmd. |
• |
PC Sol. 4 Pressure Cmd. |
• |
PC Sol. 5 Pressure Cmd. |
- Check the garage shifts.
5.1. |
Apply the brake pedal and ensure the handbrake is
set. |
5.2. |
Move the gear selector through the following
ranges: |
5.2.2. |
REVERSE to NEUTRAL |
5.3. |
Pause 2 to 3 seconds in each gear
position. |
5.4. |
Verify the gear engagements are immediate (less
than 2 seconds to complete if trans fluid temperature is above
20°C) and not harsh. Note that these shifts may be almost
imperceptible in some applications. Using the scan tool to monitor
Transmission ISS achieving 0 rpm can be used to check delay in
these cases. |
Note: Harsh engagement may be
caused by any of the following conditions:
• |
High engine idle speed-Compare
engine idle speed to desired idle speed. |
• |
Incorrect line
pressure--Investigate Line PC Sol. Pressure Cmd. kPa (psi),
also perform
Line Pressure Check . |
• |
A default condition caused by
certain DTCs that result in maximum line pressure to prevent clutch
slippage. |
• |
Incomplete adapting or
incorrect adapting--Repeat manoeuvre multiple times to see if shift
quality improves. If it does not, refer to the service procedures
for
Harsh Garage Shift . |
Note: Delayed engagement may be
caused by any of the following conditions:
• |
Low idle speed--Compare engine
idle speed to desired idle speed. |
• |
Incorrect line
pressure--Investigate Line PC Sol. Pressure Cmd. kPa (psi),
also perform
Line Pressure Check . |
• |
Cold transmission fluid
temperature (TFT)--Use the scan tool to determine TFT.
|
• |
Selector linkage--Inspect and
adjust as necessary. |
• |
Incomplete adapting or
incorrect adapting--Repeat manoeuvre multiple times to see if delay
improves. If it does not, refer to the service procedures for
Harsh First and Reverse Shift . |
- Monitor transmission range on the scan tool,
transmission data list.
6.1. |
Apply the brake pedal and ensure the handbrake is
set. |
6.2. |
Move the gear selector through all ranges. |
6.3. |
Pause 2 to 3 seconds in each range. |
6.4. |
Return gear selector to PARK. |
6.5. |
Verify that all selector positions match the scan
tool display. |
- Check throttle position input.
7.1. |
Apply the brake pedal and ensure the handbrake is
set. |
7.2. |
Ensure the gear selector is in PARK. |
7.3. |
Monitor the scan tool Calc. Throttle Position
while increasing and decreasing engine speed with the throttle
pedal. The scan tool Calc. Throttle Position percentage should
increase and decrease with engine speed. |
If any of the above checks do not perform properly, record the
result for reference after completion of the road test.
Upshift Control and Torque Converter Clutch (TCC)
Apply
The TCM calculates the upshift points based primarily on 2
inputs: throttle position and vehicle speed. When the TCM
determines that conditions are met for a shift to occur, the TCM
commands the shift by varying current to the appropriate PC
solenoids to control oncoming and off going clutch pressures.
Perform the following steps:
- Monitor the following scan tool parameters:
• |
Calc. Throttle Position |
• |
TCC PC Sol. Pressure Cmd. |
• |
PC Sol. 2 Pressure Cmd. |
• |
PC Sol. 3 Pressure Cmd. |
• |
PC Sol. 4 Pressure Cmd. |
• |
PC Sol. 5 Pressure Cmd. |
- Place the gear selector in the DRIVE position.
- Accelerate the vehicle using a steady throttle
position between 15 and 20 percent. Hold the throttle steady.
- As the transmission upshifts, there should be a
noticeable shift feel or engine speed change within 1 to
2 seconds of the commanded gear change. The PC solenoid
pressure command should change to "YES" for the oncoming clutch and
the PC solenoid pressure command should change to "NO" for the off
going clutch.
- Note any harsh, soft or delayed shifts or slipping.
Note any noise or vibration.
- The TCC feel may not be noticeable. In many
applications the TCC will apply after the 1-2 shift and TCC events
will not be easily detected using engine speed.
Note: This transmission is
equipped with an electronically controlled capacity clutch (ECCC),
which allows operation of the clutch without fully locking to the
torque converter cover. The clutch maintains a small amount of
slippage, approximately 20 RPM, in 2nd, 3rd, 4th, 5th, and 6th
gears, depending on the vehicle application. ECCC was developed to
reduce the possibility of noise, vibration or chuggle caused by TCC
apply. Full lockup is available at motorway speeds on some
applications.
- Monitor TCC PC solenoid pressure command while driving
and check TCC slip speed when the pressure command indicates that
the TCC is commanded to apply:
When the TCC applies, slip speed should be controlled to below
100 RPM when the transmission is not shifting and the throttle
is held steady. If the TCC slip exceeds this value for more than 6
seconds after the TCC PC Sol. Pressure Command indicates that the
TCC is commanded on:
Part Throttle Step-In Downshifts
- Place the gear selector in the DRIVE position.
- Accelerate the vehicle at light throttle
(5-15 percent) until 3rd gear is just achieved.
- Quickly increase throttle angle until commanded gear
indicates that a downshift to 2nd gear is commanded.
- Verify that the transmission downshifts within 2
seconds of the throttle movement.
- Repeat steps 2 to 4 at higher speed to achieve 4th
gear and then step in to command a 4th gear to 3rd gear
downshift.
- Repeat steps 2 to 4 at higher speed to achieve 5th
gear and then step in to command a 5th to 4th gear downshift.
- Repeat steps 2 to 4 at higher speed to achieve 6th
gear and then step in to command a 6th gear to 5th gear
downshift.
- Note any harsh, soft or delayed shifts or slipping.
Note any noise or vibration.
Manual Downshifts
Manual downshift testing is not required since all vehicles
equipped are also equipped with some form of Driver Shift
Control(DSC). The TCM will automatically override DSC downshifts to
protect the transmission from damage.
Coasting Downshifts
- Place the gear selector in the DRIVE position.
- Accelerate the vehicle to 6th gear with the TCC
applied.
- Release the throttle and apply the brakes
- Verify that the downshifts occur as commanded by
monitoring gear ratio, which should change after commanded gear
changes.
Manual Gear Range Selection
This application does not utilise manual forward gear
ranges.
Reverse
Perform the following test using a 10-15 percent throttle
position.
- With the vehicle stopped, move the gear selector to
REVERSE.
- Slowly accelerate the vehicle.
- Verify that there is no noticeable slip, noise or
vibration.
Driver Shift Control (DSC)
Refer to the owner's manual for specific instructions on the
type of DSC available in this application. Utilise the DSC to
ensure that the transmission responds appropriately to driver's
commands. The TCM will upshift automatically when maximum engine
speed is achieved and will protect from any downshift which may
cause excessive engine RPMs.
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