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:
• |
Visual inspection of
transmission fluid leaks |
• |
Electrical function
check |
• |
Confirm customer complaint by
driving |
• |
Check oil level and oil
quality |
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 |
• |
Vent hose is correctly
mounted. |
During the road test:
• |
Perform the test only when
traffic conditions permit |
• |
Operate the vehicle in a
controlled, safe manner |
• |
Observe all traffic
regulations. |
|
Note: Take along
qualified help in order to operate the vehicle safely.
|
• |
View the scan tool data while
conducting this test. |
• |
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.
1. |
Connect the scan tool.
|
2. |
Ensure the selector lever is
in PARK and set the parking brake. |
4. |
Verify that scan tool data can
be obtained. Refer to
Control Module References for typical data values. Data that is
questionable may indicate a concern. |
5. |
Monitor the TCC brake switch
parameter while applying and releasing the brake pedal. The scan
tool should display: |
|
• |
Open when the brake pedal is
applied. |
|
• |
Closed when the brake pedal is
released. |
6. |
Check the garage
shifts. |
|
• |
Apply the brake pedal and
ensure the parking brake is set. |
|
• |
Move the gear selector through
the following ranges: |
|
• |
Pause 2 to 3 seconds in each
shift position. |
|
Note: Harsh engagement may
be caused by any of the following conditions:
|
- |
Verify the gear engagements are immediate and
not harsh. |
|
- |
High
engine idle speed - Compare engine idle speed to desired idle
speed. |
|
- |
High
pressure will cause harsh shifts. |
|
- |
A
default condition caused by certain DTCs that result in maximum
line pressure to prevent clutch slippage. |
|
|
Note: Soft or delayed
engagement may be caused by any of the following conditions:
|
- |
Low
idle speed - Compare engine idle speed to desired idle
speed. |
|
- |
Low
pressure will cause soft or delayed shifts. |
|
- |
Cold
transmission fluid temperature (TFT) - Use the scan tool to
determine TFT. |
|
- |
Selector linkage - Inspect and adjust as
necessary. |
|
|
|
|
|
• |
Verify the gear engagements
are immediate and not harsh. |
7. |
Monitor transmission range on
the scan tool, engine data list. |
|
• |
Apply the brake pedal and
ensure the parking brake is set. |
|
• |
Move the gear selector through
all ranges. |
|
• |
Pause 2 to 3 seconds in each
range. |
|
• |
Return gear selector to
PARK. |
|
• |
Verify that all selector
positions match the scan tool display. |
8. |
Check throttle position
input. |
|
• |
Apply the brake pedal and
ensure the parking brake is set. |
|
• |
Ensure the selector lever is
in PARK. |
|
• |
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.
Adaptive Learning
Start driving the car and make the adaptive learning. Refer to
Transmission Adaptive Functions .
Confirm Customer Complaint by Driving
Continue driving to verify the customer complaint. It might be
useful to use manual shifting in order to verify the problem.
Check Oil Level and Oil Quality
After the driving is finalized and the complaint has been
recorded:
|
- |
If the oil is
milky there is a water leakage into the transmission. Check the
vent hose. |
|
- |
If the oil smells
burnt and its color is dark some disc may have been
overloaded. |
• |
If the oil quality is too bad,
change oil, make a new adaptive driving and the check if the
problem is still there. |
|