• | Perform the road test using a scan tool. |
• | Perform this test when the traffic and the road conditions permit.
Observe all safety regulations. |
- Start the engine.
- Depress the brake pedal.
Important: Gear selections should be immediate and not harsh.
- Move the gear selector as follows:
- Perform the same procedure as instructed previously in the road
test:
• | Upshifts and TCC apply. |
• | The part throttle detent downshift |
• | The full throttle detent downshift |
• | Manual gear range selection |
Use the scan tool in order to see if any transmission malfunction codes
have been set. If so, perform the transmission test. After repairing the vehicle,
perform the road test and verify that no codes have been set again. If no
codes have been set and the condition remains, refer to the Diagnosis Tables
contained in this section. If the condition is suspected to originate in the
torque converter, refer to Torque Converter Clutch (TCC) Diagnosis
.
Upshift Control and TCC Apply
The PCM calculates the upshift points based primarily on two inputs:
THROTTLE ANGLE and VEHICLE SPEED. When the PCM says a shift should occur,
an electrical signal goes to the shift solenoids which in turn move the valves
to perform the upshift.
The shift speed tables reference the THROTTLE ANGLE instead of MIN THROTTLE
or WOT in order to make the shift speed measurement more uniform and accurate.
Use a Scan Tool
in order
to monitor the THROTTLE ANGLE. Some scan tools are programmed to record shift
point information. Check the instruction manual in order to see if this test
is available.
With the gear selection in D4, do the following:
- Look at the
Shift Speed
table contained in this section and choose a throttle angle of 15
or 20 percent.
- Set up the Scan Tool
in order to monitor the THROTTLE ANGLE and the VEHICLE SPEED.
- Accelerate to the chosen throttle angle and hold the throttle
steady.
Important: Shift speeds may vary due to the slight hydraulic delays responding
to electronic controls. A change from the original equipment tire size also
affects the shift speeds.
Note when the TCC applies. This should occur in third or fourth gear.
If the apply is not noticed by an RPM drop, refer to the Torque Converter Clutch (TCC) Diagnosis
.
The TCC should not apply unless the transmission has reached a minimum
operating temperature of 18°C (64°F) Trans. Fluid Temp. and an Engine
Coolant Temperature (ECT) of 60°C (140°F).
- As the transmission upshifts, note the shift speed and the commanded
gear changes for the following:
- Repeat steps 1-4, using several different throttle angles.
Full Throttle Detent Downshift
At vehicle speeds of 64-88 km/h (40-55 mph)
in fourth gear, quickly increase the throttle angle to the maximum position.
Verify that the following conditions are met:
• | The transmission downshifts to 2rd gear immediately. |
• | The 1-2 shift solenoid turns off. The 2-3 shift solenoid is on. |
Part Throttle Detent Downshift
At vehicle speeds of 64-88 km/h (40-55 mph)
in fourth gear, quickly increase the throttle angle.
Verify that the following conditions are met:
• | The transmission downshifts to 3rd gear immediately. |
• | The 1-2 shift solenoid turns off. |
Coasting Downshifts
- With the gear selector in D4, accelerate to the 4th gear with
the TCC applied.
- Release the accelerator pedal. Lightly apply the brakes. Observe
that the following occurs:
• | The downshifts occur at speeds shown on the
Shift Speed
table. |
Manual Downshifts
The shift solenoids do not control the initial downshift during the
4-3 and the 3-2 manual downshifts. All manual downshifts are hydraulic except
the 2-1. The solenoid states will change during or shortly after a manual
downshift is selected.
- At vehicle speeds of 64-88 km/h (40-55 mph)
in fourth gear, release the accelerator pedal while moving the gear selector
to D3. Observe the following:
• | The transmission downshifts to 3rd gear immediately. |
• | The engine slows down the vehicle. |
- Move the gear selector back to D4 and accelerate to 64-72 km/h
(40-45 mph). Release the accelerator while moving the gear selector
to D2 and observe that:
• | The transmission downshifts to the 2nd gear immediately. |
• | The engine slows down the vehicle. |
- Move the gear selector back to D4 and accelerate to 48 km/h
(30 mph). Release the accelerator pedal while moving the gear selector
to D1 and observe the following conditions:
• | The transmission downshifts to 1st gear immediately. |
• | The engine slows down the vehicle. |
Manual Gear Range Selection
Upshifts in the manual gear ranges are controlled by the shift solenoids.
Perform the following tests by accelerating at 10-15 degrees
TP Sensor.
With the vehicle stopped, move the gear selector to D3 and accelerate
in order to observe:
Manual Third (D3)
Manual Second (D2)
- With the vehicle stopped, move the gear selector to the D2 position
and accelerate in order to observe if the transmission starts and remains
in second gear.
- Accelerate to 40 km/h (35 mph) and observe the following:
• | The 2-3 shift does not occur. |
• | The TCC does not apply. |
Manual First (D1)
- With the vehicle stopped, move the gear selector to D1.
- Accelerate to 32 km/h (20 mph).
- Observe the following conditions:
• | The TCC does not apply. |
• | You can upshift out of first at the fuel cut-off. |
Reverse
With the engine stopped, move the gear selector to R and slowly accelerate
in order to observe that the 1-2 and 2-3 shift solenoids are ON.
Use a scan tool in order to see if any transmission trouble codes have
been set. Refer to Trouble Codes Diagnosis in this section and repair the
vehicle as directed. After repairing the vehicle, perform the hoist test and
verify that the code has not set again.
If the transmission is not performing well and no trouble codes have
been set, there may be an intermittent condition. Check all electrical connections
for damage or a loose fit. Some scan tools have a snapshot test which can
help catch an intermittent condition that doesn't occur long enough to set
a code.
You may want to read
Electronic Component Description
in this
section in order to become familiar with the transmission conditions caused
by transmission electrical malfunctions.
If no trouble codes have been set and the condition is suspected to
be hydraulic, take the vehicle on a road test.