Circuit Description
The 1-2 shift solenoid (SS) valve is a normally-open exhaust valve that,
in conjunction with the 2-3 shift solenoid (SS) valve, allows 4 different
shifting combinations. The 1-2 SS valve is attached to the lower
control valve body, within the transmission.
The PCM monitors the actual gear ratio, and compares the actual gear
ratio with the commanded gear ratio. DTC P0751 sets under two conditions:
| • | A stuck OFF 1-2 SS valve |
| • | A stuck OFF 1-2 shift valve |
If the PCM detects a 2-2-3-3 shift pattern, then DTC P0751 sets.
DTC P0751 is a type B DTC.
Conditions for Running the DTC
| • | No TP DTCs P0121, P0122 or P0123. |
| • | No VSS DTCs P0502 or P0503. |
| • | No AT ISS DTCs P0716 or P0717. |
| • | No IMS DTCs P1820, P1822, P1823 or P1825. |
| • | No shift solenoid electrical DTCs P1842, P1843, P1845 or
P1847. |
| • | The engine run time is greater than 5 seconds. |
| • | The IMS indicates D1, D2, D3 or D4. |
| • | The transmission fluid temperature is 20-133°C (68-271°F). |
| • | The TP angle is 7.5% or greater. |
| • | The vehicle speed is 8 km/h (5 mph) or greater. |
| • | The engine torque is 80-395 N·m (59-291 lb ft). |
Conditions for Setting the DTC
The following conditions occur twice during the same trip:
| • | The PCM commands 1st gear and the gear ratio is 1.54:1-1.71:1
(2nd gear) for 1.5 seconds. |
| • | The PCM commands 4th gear and the gear ratio is 0.95:1-1.05:1
(3rd gear) for 4 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during
the second consecutive trip in which the Conditions for Setting the DTC are
met. |
| • | The PCM commands maximum line pressure. |
| • | The PCM inhibits TCC engagement. |
| • | The PCM freezes transmission adapt functions. |
| • | The PCM records the operating conditions when the Conditions for
Setting the DTC are met. The PCM stores this information as Freeze Frame and
Failure Records. |
| • | The PCM stores DTC P0751 in PCM history during the second consecutive
trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The PCM 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 PCM clears the DTC from PCM history if the vehicle completes
40 warm-up cycles without an emission-related
diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the ignition switch
is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | If you clear DTC P0751, and then cannot reset DTC P0751,
the following conditions may exist: |
| - | Restricted fluid circuits |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies
a 2-2-3-3 shift pattern.
-
This step tests
for a mechanical or hydraulic condition causing the 1-2 SS valve to be stuck
OFF, or the circuit to be released.
DTC P0751 1-2 Shift Solenoid Valve -- Performance
Step
| Action
| Value(s)
| Yes
| No
|
1
| Did you perform the Powertrain Diagnostic System Check?
| --
|
Go to Step 2
| Go to
Diagnostic System Check - Engine Controls
in Engine
Controls
|
2
| Did you perform the Transmission Fluid Checking Procedure?
| --
|
Go to Step 3
| Go to
Transmission Fluid Check
|
3
|
- Install a Scan Tool
.
- Turn ON the ignition, with the engine OFF.
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 PCM.
- Record the DTC Freeze Frame and Failure Records.
- Clear the DTC.
- Use the scan tool snapshot mode in order to record current gear
and gear ratio.
- Drive the vehicle in D4, in order to obtain 1-2, 2-3 and 3-4 shifts
with a TP angle of 7.5% or greater.
Are the current gear and gear ratio within the specified parameters?
| 1st/2nd
1.54:1-1.71:1
3rd/4th
0.95:1-1.05:1
|
Go to Step
4
| Go to Diagnostic Aids
|
4
|
- Inspect the 1-2 shift circuit for the following conditions:
| • | 1-2 SS valve mechanically stuck OFF. |
| • | 1-2 SS valve O-ring worn or damaged. |
| • | 1-2 shift valve stuck in the released position. |
- Repair the circuit as necessary.
Refer to
Transmission Overhaul
in Transmission Unit Repair Manual.
Did you complete the repair?
| --
|
Go to Step
5
| --
|
5
| Perform the following procedure in order to verify the
repair:
- Select DTC.
- Select Clear Info.
- Operate the vehicle under the following conditions:
| • | Drive the vehicle in D4 with a TP angle of 7.5% or greater. |
| • | Allow the transmission to shift through all the gears. |
| • | Monitor the current gear and gear ratios. The actual gear ratios
must match the commanded gears for 0.75 seconds, for all gears. |
- Select Specific DTC.
- Enter DTC P0751.
Has the test run and passed?
| --
| System OK
|
Go to Step
1
|
