4T45-E Automatic Transaxle
DTC P1750
Circuit 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. DTC P1750 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1750 1-2 Shift Valve Performance
Conditions for Running the DTC
* No ISS DTCs P0716 or P0717.
* No OSS DTCs P0722 or P0723.
* The engine is running for 5 seconds.
* The vehicle speed is greater than 24 km/h (15 mph).
* The calc. throttle position is greater than 8 percent.
* The transmission fluid temperature 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 does not request the ECM to illuminate the malfunction indicator lamp (MIL).
* 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 freezes transmission adaptive functions.
* 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 records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
* The TCM stores DTC P1750 in TCM history.
Conditions for Clearing the DTC
* 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 DTC default actions when the fault no longer exists an d the DTC passes.
Diagnostic Aids
If DTC P1750 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
