DTC P0751 4.2L
Circuit Description
The 1-2 shift solenoid (SS) valve controls the fluid flow acting on the
1-2 and 3-4 shift valves. The 1-2 SS valve is a normally-open
exhaust valve that is used with the 2-3 SS valve, in order to allow 4 different
shifting combinations.
If the powertrain control module (PCM) detects a 2-2-3-3 shift pattern,
then DTC P0751 sets. DTC P0751 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0751 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
Conditions for Running the DTC
| • | No VSS DTCs P0502 or P0503. |
| • | No TCC stuck ON DTC P0742. |
| • | No 1-2 SS valve DTC P0753. |
| • | No 2-3 SS valve DTC P0758. |
| • | No TP sensor DTCs P1120 or P1220. |
| • | The engine speed is greater than 450 RPM for 5 seconds. |
| • | The engine is not in fuel cutoff. |
| • | The TP angle is 10 percent or greater. |
| • | The transmission fluid temperature is 20-130°C (68-266°F). |
| • | The system voltage is 10-18 volts. |
| • | The engine torque is 68-542 N·m (50-400 lb ft). |
| • | The transmission output speed is 150 RPM or greater. |
| • | The transfer case ratio in 4WD Low is 0.9 to 1.2. |
| • | The transfer case ratio in 4WD High is 2.6 to 2.85. |
Conditions for Setting the DTC
DTC P0751 sets if both of the following conditions occur twice:
Condition 1
| • | The PCM commands first gear for 2 seconds. |
| • | The estimated gear ratio is 1.2-1.8. |
| • | The torque converter efficiency is greater than or equal to 0.35. |
| • | All conditions are met for 0.5 seconds. |
Condition 2
| • | The PCM commands fourth gear for 1 second. |
| • | The estimated gear ratio is 0.95-1.15. |
| • | All conditions are met for 6 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 D2 line pressure. |
| • | The PCM commands TCC OFF. |
| • | The PCM inhibits fourth gear in hot mode. |
| • | The PCM freezes transmission adaptive 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. |
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 fault no longer exists
and/or the ignition switch is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Verify that the transmission meets the specifications in the
Shift Speed table. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests that the PCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.
DTC P0751 (4.2L)
Step
| Action
| Yes
| No
|
1
| Did you perform the Diagnostic System Check - Vehicle?
| Go to
Step 2
| Go to
Diagnostic System Check - Vehicle
in Vehicle DTC Information
|
2
|
- 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 powertrain control module (PCM).
- 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 PCM commands 1st, 2nd, 3rd and 4th gears.
Did you detect a 2-2-3-3 shift pattern?
| Go to
Step 3
| Go to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems
|
3
| Inspect the shift solenoid/hydraulic circuit for the following conditions:
| • | An internal malfunction |
| • | Damaged seals on the shift solenoid valve |
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 range under the following conditions, only if traffic and road conditions permit:
Hold the throttle at 20 percent and accelerate to 88 km/h (55 mph).
- Select Specific DTC.
- Enter DTC P0751.
Has the test run and passed?
| Go to
Step 5
| Go to
Step 2
|
5
| With the scan tool, observe the stored information, capture info, and DTC Info.
Does the scan tool display any DTCs that you have not diagnosed?
| Go to
Diagnostic Trouble Code (DTC) List - Vehicle
in Vehicle DTC Information
| System OK
|
DTC P0751 5.3L and 6.0L
Circuit Description
The 1-2 shift solenoid (SS) valve controls the fluid flow acting on the
1-2 and 3-4 shift valves. The 1-2 SS valve is a normally-open
exhaust valve that is used with the 2-3 SS valve, in order
to allow 4 different shifting combinations.
If the transmission control module (TCM) detects a 2-2-3-3 shift pattern, then
DTC P0751 sets. DTC P0751 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0751 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
Conditions for Running the DTC
| • | No input speed sensor (ISS) DTCs P0716 or P0717. |
| • | No output (shaft) speed sensor (OSS) DTCs P0722 or P0723. |
| • | No torque converter clutch (TCC) performance DTC P0742, P0894. |
| • | No shift solenoid electrical DTCs P0973, P0974, P0976, or P0977. |
| • | The ignition voltage is 8-18 volts. |
| • | The engine RPM is 500-6,500 RPM for greater than 5 seconds. |
| • | The transmission fluid temperature is 20-130°C (68-266°F). |
| • | The throttle position is 10 percent or greater. |
| • | The output shaft speed is 150 RPM or greater. |
Conditions for Setting the DTC
Both of the following conditions must occur twice during the same trip:
| • | Fail Case 1: The TCM commands 1st gear and the resulting gear ratio is
1.23:1-1.84:1 for 0.5 seconds. |
| • | Fail Case 2: The TCM commands 4th gear and the resulting gear ratio is
0.95:1-1.15:1 for 1 second. |
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp
(MIL) during the second consecutive trip in which the Conditions for Setting the DTC
are met. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | At the time of the first failure, the TCM records the operating conditions
when the Conditions for Setting the DTC are met. The TCM stores this information as
a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions
when the Conditions for Setting the DTC are met. The ECM stores this information as
a Freeze Frame. |
| • | The TCM stores DTC P0751 in TCM history during the second consecutive
trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. |
| • | The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM. |
Diagnostic Aids
| • | If you clear DTC P0751, and then cannot reset DTC P0751,
the following conditions may exist: |
| - | Restricted fluid circuits |
Test Description
The number below refers to the step number on the diagnostic table.
-
This step tests that the TCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.
DTC P0751
Step
| Action
| Yes
| No
|
1
| Did you perform the Diagnostic System Check - Vehicle?
| Go to
Step 2
| Go to
Diagnostic System Check - Vehicle
|
2
|
- 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 transmission control module (TCM).
- 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 TCM commands 1st, 2nd, 3rd, and 4th gears.
Did you detect a 2-2-3-3 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 valve |
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 range under the following conditions, only if traffic and road conditions permit:
Hold the throttle at 20 percent and accelerate to 88 km/h (55 mph).
- Select Specific DTC.
- Enter DTC P0751.
Has the test run and passed?
| Go to
Step 5
| Go to
Step 2
|
5
| With the scan tool, observe the stored information, capture info, and DTC Info.
Does the scan tool display any DTCs that you have not diagnosed?
| Go to
Diagnostic Trouble Code (DTC) List - Vehicle
| System OK
|
