DTC P0756 2-3 (B) Shift Solenoid Performance 6.5L Diesel
Circuit Description
The 2-3 SS Valve controls fluid flow acting on the 2-3 shift valves. The 2-3 SS Valve is a normally-open exhaust valve used with the 1-2 shift solenoid valve to allow four different shift combinations.
When the PCM detects a non first gear ratio while first gear is commanded or a first gear ratio while fourth gear is commanded, then DTC P0756 sets. DTC P0756 is a type A DTC.
Conditions for Setting the DTC
| • | No APP DTCs P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, or P0228. |
| • | No engine speed DTC P0219. |
| • | No OSS Sensor DTCs P0722 or P0723. |
| • | No TFT Sensor DTCs P0712 or P0713. |
| • | No 4WD Lo DTC P1875. |
| • | No TFP Val. Position Sw. DTC P1810. |
| • | No shift solenoid electrical DTCs P0753 or P0758. |
| • | No ISS Sensor DTCs P0716 or P0717. |
| • | The engine is running. |
| • | The vehicle speed is greater than 6 km/h (4 mph). |
| • | The throttle position is greater than 12%. |
| • | The transmission fluid temperature is 20-130°C ( 68-266°F ). |
| • | The engine torque is 100-565 N·m (80-450 lb ft). |
| • | The engine speed is less than 3750 RPM. |
| • | All of the above conditions are met and either of the two following conditions occur: |
| - | When the 2-3 Solenoid valve is stuck on, the commanded gear equals 1st and the ratio equals 4th for greater than 2 seconds, and the commanded gear equals 2nd and the ratio equals 3rd for greater than 2 seconds. The conditions occur for 4 occurrences. |
| - | When the 2-3 SS Valve is stuck off, the commanded gear equals 3rd and the ratio equals 2nd for greater than 3 seconds. The condition occurs for 8 occurrences with a continual rolling counter. |
Action Taken When the DTC Sets
| • | The transmission immediately lands to 2nd gear. |
| • | The PCM commands maximum line pressure. |
| • | The PCM freezes shift adapts. |
| • | The PCM illuminates the Malfunction Indicator Lamp (MIL). |
Conditions for Clearing the MIL/DTC
- A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM
Diagnostic Aids
| • | Verify that the transmission meets the specifications in the 4L80-E shift speed table. |
| • | Other internal transmission failures may cause more than one shift to occur. |
| • | The customer may complain of an engine over-rev condition or neutral condition in 4th gear. |
| • | First diagnose and clear any engine DTCs or APP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
Refer to Shift Solenoid Valve State and Gear Ratio table.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the function of the TFP Val. Position Sw.
-
This step tests for a selected gear ratio versus a ratio not obtainable under normal driving conditions.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does each selected transmission range match the Trans Range on the scan tool? | -- | |||||||
Was 1st gear commanded and not achieved, or 4th gear commanded and another gear occurred? You may need to road test the vehicle. | -- | Go to Diagnostic Aids | ||||||
4 |
Did you find and correct a problem? | -- | -- | |||||
5 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
DTC P0756 2-3 (B) Shift Solenoid Performance 4.3L, 5.7L, and 7.4L Gas
Circuit Description
The 2-3 shift solenoid valve controls fluid flow acting on the 2-3 shift valves. The solenoid is a normally-open exhaust valve used with the 1-2 shift solenoid valve to allow for four different shift combinations.
When the VCM detects a non first gear ratio while first gear is commanded or a first gear ratio while fourth gear is commanded, then DTC P0756 sets. When the VCM detects a second gear ratio while third gear is commanded, then DTC P0756 sets. DTC P0756 is a type D DTC. For California emissions vehicles, DTC P0756 is a type A DTC.
Conditions for Setting the DTC
| • | No TP Sensor DTCs P0121, P0122, or P0123. |
| • | No VSS DTCs P0502. |
| • | No TFP Val. Position Sw. DTC P1810. |
| • | No shift solenoid electrical DTCs P0753 or P0758. |
| • | No ISS Sensor DTCs P0716 or P0717. |
| • | The engine runs for 5 seconds and not be in fuel cut off. |
| • | The vehicle speed is greater than 6 km/h (4 mph). |
| • | The throttle position is greater than 12%. |
| • | The transmission fluid temperature is 20-130°C ( 68-266°F ). |
| • | The engine torque is 100 N·m (80 lb ft) to the following: |
| - | 345 N·m (275 lb ft) 4.3L |
| - | 470 N·m (375 lb ft) 5.7L |
| - | 627 N·m (500 lb ft) 7.4L. |
| • | All of the above conditions are met and either of the two following conditions occur: |
| - | When the 2-3 Solenoid valve is stuck on, the commanded gear equals 1st and the ratio equals 4th for greater than 2 seconds, and the commanded gear equals 2nd and the ratio equals 3rd for greater than 2 seconds. The conditions occur for 2 occurrences ( 3 occurrences for the 4.3L). |
| - | When the 2-3 SS Valve is stuck off, the commanded gear equals 3rd and the ratio equals 2nd for greater than 3 seconds. The condition occurs for 4 occurrences with a continual rolling counter (5 occurrences for the 4.3L). |
Action Taken When the DTC Sets
| • | The transmission immediately lands to 2nd gear. |
| • | The VCM commands maximum line pressure. |
| • | The VCM freezes shift adapts. |
| • | The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles. |
Conditions for Clearing the MIL/DTC
- For California emissions vehicles, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
- A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.
Diagnostic Aids
| • | Verify that the transmission meets the specifications in the 4L80-E shift speed table. |
| • | Other internal transmission failures may cause more than one shift to occur. |
| • | The customer may complain of an engine over-rev condition or neutral condition in 4th gear. |
| • | First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
Refer to Shift Solenoid Valve State and Gear Ratio table.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the function of the TFP Val. Position Sw.
-
This step tests for a selected gear ratio versus a ratio not obtainable under normal operating conditions.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check (4.3L) or Powertrain On Board Diagnostic (OBD) System Check (5.7L and 7.4L) | |||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does each selected transmission range match the Trans Range on the scan tool? | -- | |||||||
Was 1st gear commanded and not achieved, or 4th gear commanded and another gear occurred? You may need to road test the vehicle. | -- | Go to Diagnostic Aids | ||||||
4 |
Did you find and correct a problem? | -- | -- | |||||
5 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
