Diagnostic Instructions
DTC Descriptor
DTC P1750: 1-2 Shift Valve Performance
Circuit/System Description
The 1-2 shift valve is used to direct fluid for shifting between 1st and 2nd gears. In 1st gear, the 1-2 shift solenoid (SS) valve is commanded ON causing 1-2, 3-4 signal fluid pressure to overcome the 1-2 shift valve spring force, moving the 1-2
shift valve into a position that routes D4 fluid into the Low/1st fluid passage. In 2nd gear, the 1-2 SS valve is commanded OFF allowing 1-2, 3-4 signal fluid to be exhausted and the 1-2 shift valve spring force then moves the 1-2 shift valve into a position
that routes D4 fluid into the 2nd fluid passage.
If the transmission control module (TCM) detects a 1st gear ratio when 2nd gear is commanded indicating a stuck 1-2 shift valve, then DTC P1750 sets.
Conditions for Running the DTC
| • | No ISS DTCs P0716 or P0717. |
| • | No OSS DTCs P0722 or P0723. |
| • | The engine is running for 2 seconds or more. |
| • | The vehicle speed is greater than 24 km/h (15 mph). |
| • | The calc. throttle position is greater than 8 percent. |
| • | The transmission fluid temperature (TFT) is 20°C (68°F) or more. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The time since the last gear change is 2 seconds. |
Conditions for Setting the DTC
The TCM commands 2nd gear and the gear ratio is 2.81:1-3.10:1 for 3.25 seconds.
Action Taken When the DTC Sets
| • | The TCM commands maximum line pressure. |
| • | The TCM inhibits 3-2 downshifts when the vehicle speed is greater than 52 km/h (32 mph). |
| • | The TCM disables TAP shift operation. |
| • | The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
| • | The TCM freezes transmission adaptive functions. |
Conditions for Clearing the DTC
DTC P1750 is a Type C DTC.
Diagnostic Aids
| • | When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions. Ensure the transmission fluid level is correct and there are no leaks. |
| • | If DTC P0752 is also set, diagnose that DTC first. |
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
- Perform the
Transmission Fluid Check
to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.
- Operate the vehicle in drive with the calculated throttle position greater than 8 percent and ensure the TCC is commanded ON and OFF a minimum of 5 times. The DTC should not set.
| ⇒ | If a DTC sets, inspect the lower control valve body for a stuck 1-2 shift valve/hydraulic circuit for a stuck or binding 1-2 shift valve, debris or damage and repair or replace as necessary. |
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
