Circuit Description
The 2-3 shift solenoid (SS) valve controls the fluid flow acting on
the 2-3 shift valves. The solenoid is a normally-open exhaust valve. With
the 1-2 SS valve, the 2-3 SS valve allows four different shifting combinations.
When the VCM detects a 1-2-2-1 or a 4-3-3-4 shift pattern, depending
on the state of the mechanical failure, then DTC P0756 sets. DTC P0756
is a type A DTC.
Conditions for Running the DTC
| • | No TP sensor DTCs P0122 or P0123. |
| • | No VSS assembly DTCs P0502 or P0503. |
| • | No TFT sensor DTCs P0711, P0712 or P0713. |
| • | No TCC solenoid valve DTC P0740. |
| • | No TCC stuck ON DTC P0742. |
| • | No 1-2 SS valve DTC P0753. |
| • | No 2-3 SS valve DTC P0758. |
| • | No 3-2 SS valve assembly DTC P0785. |
| • | No TFP manual valve position switch DTC P1810. |
| • | No TCC PWM solenoid valve DTC P1860. |
| • | The vehicle speed is greater than 8 km/h (5 mph). |
| • | The TP angle is 15-50%. |
| • | The TP angle is constant within +/- 7%. |
| • | The engine vacuum is 0-105 kPa. |
| • | The engine torque is 5-450 lb ft. |
| • | The engine speed is greater than 450 RPM for 5 seconds. |
| • | The engine is not in fuel cutoff. |
| • | The transmission fluid temperature is 20-130°C (68-266°F). |
| • | The VCM commands a 1-2, 2-3 and 3-4 shift. |
Conditions for Setting the DTC
DTC P0756 sets if the following conditions occur three times:
| • | Third gear is commanded for 2 to 5 seconds. |
| • | The speed ratio in 3rd gear does not drop more than 0.3 from the
last speed ratio in 2nd gear (speed ratio is engine speed divided by transmission
output speed). |
| • | The TCC slip speed in 3rd gear remains 300 RPM higher than
the last TCC slip speed in 2nd gear. |
All of the above conditions are met for 1.5 seconds and one of
the following conditions occurs:
Condition 1
| • | First gear is commanded for 2 seconds. |
| • | The transmission output speed is 400-1500 RPM. |
| • | The speed ratio is 0.5 to 3.0. |
| • | The TCC slip speed is -3000 to -100 RPM for
1 second. |
Condition 2
| • | Fourth gear is commanded for 1 second. |
| • | The transmission output speed is 1400-2500 RPM. |
| • | The speed ratio is 2.05 to 8. |
| • | The TCC slip speed is 1000 to 4000 RPM for 1 second. |
Action Taken When the DTC Sets
| • | The VCM illuminates the malfunction indicator lamp (MIL). |
| • | The VCM commands third gear only. |
| • | The VCM inhibits TCC engagement. |
| • | The VCM commands maximum line pressure. |
| • | The VCM freezes shift adapts from being updated. |
| • | The VCM records the operating conditions when the Conditions for
Setting the DTC are met. The VCM stores this information as Freeze Frame and
Failure Records. |
| • | The VCM stores DTC P0756 in VCM history. |
Conditions for Clearing the MIL/DTC
| • | The VCM turns OFF the MIL during the third consecutive trip in
which the diagnostic test runs and passes. |
| • | A scan tool can clear the MIL/DTC. |
| • | The VCM clears the DTC from VCM history if the vehicle completes
40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The VCM cancels the DTC default actions when the fault no longer
exists and/or the ignition switch is OFF long enough in order
to power down the VCM. |
Diagnostic Aids
| • | Verify that the transmission meets the specifications in the
Shift Speed
table. |
| • | Ensure that the proper transmission oil filter assembly is being
used in conjunction with the applicable transmission oil pan. |
| • | Other internal transmission failures may cause more than one shift
to occur. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the VCM commanded all shifts, that all shift
solenoids responded correctly, but all the shifts did not occur.
DTC P0756 2-3 SS Valve Performance
Step
| Action
| Value(s)
| Yes
| No
|
1
| Was the Powertrain On-Board Diagnostic (OBD) System Check
performed?
| --
|
Go to Step
2
| Go to
Powertrain On Board Diagnostic (OBD) System Check
in Engine Controls
|
2
|
- Install a Scan Tool
.
- With the engine OFF, turn the ignition switch to the RUN position.
Important: Before clearing the DTC, use the Scan Tool
in order to record the Freeze Frame and Failure Records.
Using the Clear Info function erases the Freeze Frame and Failure Records
from the VCM.
- Record the DTC Freeze Frame and Failure Records.
- Clear the DTC.
- Drive the vehicle in D4 range, under the following conditions:
Accelerate the vehicle, ensuring that the VCM commands 1st, 2nd, 3rd,
and 4th gears.
Did you detect a 1-2-2-1 or 4-3-3-4
shift pattern?
| --
|
Go to Step 3
| Go to Diagnostic Aids
|
3
| Inspect the shift solenoid/hydraulic circuit for the following
conditions:
| • | An internal malfunction |
| • | Damaged seals on the shift solenoid valves. |
| | Refer to Shift Solenoid Leak Test
. |
Did you find and correct the condition?
| --
|
Go to Step 4
| --
|
4
| Perform the following procedure in order to verify the
repair:
- Select DTC.
- Select Clear Info.
- Drive the vehicle in D4 under the following conditions (only if
traffic and road conditions permit):
| • | Hold the throttle at 50% and accelerate to 64 km/h (40 mph). |
| • | Stop the vehicle, engine idling. |
| • | Hold the throttle at 25% and accelerate to 80 km/h (50 mph). |
- Select Specific DTC.
- Enter DTC P0756.
Has the test run and passed?
| --
| System OK
|
Go to Step 1
|
