DTC P0751 3.8L
Circuit Description
The 1-2 shift solenoid (1-2 SS) valve is supplied with fused ignition voltage. The ground path is controlled by the PCM. When the PCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the PCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.
The PCM identifies a 1-2 SS valve condition by monitoring the commanded gear versus gear ratio. Refer to Shift Solenoid Valve State and Gear Ratio .
If the PCM detects a 2nd gear ratio when 1st gear is commanded and a 3rd gear ratio when 4th gear is commanded, 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 (SS) Valve Performance - No First or Fourth Gear
Conditions for Running the DTC
| • | No VSS DTC P0502 or P0503. |
| • | No ISS DTC P0716 or P0717. |
| • | No TCC system stuck ON DTC P0742. |
| • | No 1-2 SS valve electrical DTC P0753. |
| • | No 2-3 SS valve electrical DTC P0758. |
| • | No TCC PWM solenoid valve DTC P2761. |
| • | The engine speed is greater than 500 RPM for 5 seconds and not in fuel cut off. |
| • | The transmission fluid temperature is between 20°C (68°F) and 130°C (266°F). |
| • | The transmission ISS is 150 RPM or more. |
| • | The transmission OSS is 300 RPM or more. |
| • | The time since the last gear range change is 1 second or more. |
Conditions for Setting the DTC
The following conditions both occur twice in one trip:
Condition 1
The PCM commands 1st gear with the TP indicated angle is 5 percent or more, the engine torque is 27-271 N·m (20-200 lb ft) and the gear ratio indicates 2nd gear, 1.52:1 to 1.60:1, for 1 second.
Condition 2
The PCM commands 4th gear with the TP indicated angle is 10 percent or more, the engine torque is 41-271 N·m (30-200 lb ft) and the gear ratio indicates 3rd gear, 0.95:1 to 1.05:1, for 1 second.
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 TAP shift operation, if equipped. |
| • | 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 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 DTC P0751 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist:
| • | Fluid contamination |
| • | Plugged fluid circuits |
| • | Restricted fluid circuits |
| • | Intermittent short to voltage in the signal circuit |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||
2 | Did you perform the Transmission Fluid Checking Procedure? | -- | Go to Step 3 | Go to Transmission Fluid Check | ||||||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear DTC Information function will erase the stored Freeze Frame and Failure Records from the PCM. Did the gear ratios indicate a 2-2-3-3 shift pattern? | 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: 0.95:1 to 1.05:1 4th: 0.65:1 to 0.75:1 | Go to Step 4 | Go to Diagnostic Aids | |||||||||||
4 |
Does the test lamp turn ON and OFF? | -- | Go to Step 6 | Go to Step 5 | ||||||||||
5 | Test the control circuit of the 1-2 SS valve for a short to voltage between the PCM and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||||
6 |
Does the resistance measure within the specified range? | 19-31 ohms | Go to Step 7 | Go to Step 8 | ||||||||||
7 | Measure the resistance from the 1-2 SS valve control circuit and all other terminals of the A/T inline 20-way connector. Refer to Testing for Continuity . Did you find a condition? | 10 Kohms | Go to Step 10 | Go to Step 11 | ||||||||||
8 |
Is the resistance within the specified range? | 19-31 ohms | Go to Step 10 | Go to Step 9 | ||||||||||
9 | Replace the 1-2 SS valve. Refer to 1-2 Shift Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
10 | Replace the AT wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
11 | Inspect the 1-2 shift solenoid valve/hydraulic circuit for the following conditions:
Refer to: Did you find and correct the condition? | -- | Go to Step 13 | -- | ||||||||||
12 | Replace the PCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
13 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: 0.95:1 to 1.05:1 4th: 0.65:1 to 0.75:1 | Go to Step 14 | Go to Step 2 | ||||||||||
14 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
DTC P0751 5.3L
Circuit Description
The 1-2 shift solenoid (1-2 SS) valve is supplied with fused ignition voltage. The ground path is controlled by the TCM. When the TCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the TCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.
The TCM identifies a 1-2 SS valve condition by monitoring the commanded gear versus gear ratio. Refer to Shift Solenoid Valve State and Gear Ratio .
If the TCM detects a 2nd gear ratio when 1st gear is commanded and a 3rd gear ratio when 4th gear is commanded, 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 TP sensor DTC P0120 or P0220. |
| • | No ISS DTC P0716 or P0717. |
| • | No OSS DTC P0722 or P0723. |
| • | No TCC system stuck ON DTC P0742. |
| • | No 1-2 SS valve electrical DTC P0973 or P0974. |
| • | No 2-3 SS valve electrical DTC P0976 or P0977. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The calc. throttle position is 8 percent or more. |
| • | The transmission fluid temperature is between 20°C (68°F) and 130°C (266°F). |
| • | The engine torque is greater than 50 N·m (37lb ft). |
| • | The transmission ISS is 150 RPM or more. |
| • | The transmission OSS is 53 RPM or more. |
| • | The time since the last gear change is 1.5 seconds. |
Conditions for Setting the DTC
The following conditions both occur twice in one trip:
Condition 1
The TCM commands 1st gear and the gear ratio indicates 2nd gear, 1.48:1 to 1.65:1, for 2 seconds.
Condition 2
The TCM commands 4th gear and the gear ratio indicates 3rd gear, 0.95:1 to 1.05:1, for 3 seconds.
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 disables TAP shift operation, if equipped. |
| • | The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Freeze Frame and Failure Records. |
| • | 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 MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive trip in which the TCM does not send an MIL illumination request. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Diagnostic Aids
If DTC P0751 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist:
| • | Fluid contamination |
| • | Plugged fluid circuits |
| • | Restricted fluid circuits |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 | Did you perform the Transmission Fluid Checking Procedure? | -- | Go to Step 3 | Go to Transmission Fluid Check | ||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the TCM. Did the gear ratios indicate a 2-2-3-3 shift pattern? | 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: 0.95:1 to 1.05:1 4th: 0.65:1 to 0.75:1 | Go to Step 4 | Go to Diagnostic Aids | |||||||
4 | Inspect the 1-2 shift solenoid valve/hydraulic circuit for the following conditions:
Refer to: Did you find and correct the condition? | -- | Go to Step 5 | -- | ||||||
5 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: 0.95:1 to 1.05:1 4th: 0.65:1 to 0.75:1 | Go to Step 6 | Go to Step 2 | ||||||
6 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
