P1750
DTC P1750 (5.3L)
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 (1-2 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 Lo/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 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 DTC P0716 or P0717.
^ The engine speed is greater than 500 RPM for 5 seconds.
^ The vehicle speed is 24 km/h (15 mph) or more.
^ The calc. throttle position is 8 percent or more.
^ The transmission fluid temperature is 20°C (68°F) or more.
^ The engine torque is greater than 50 Nm (37 ft. lbs.).
Conditions for Setting the DTC
The TCM commands 2nd gear for 2 seconds or more and the ratio indicates 1st gear, 2.87:1 to 2.97:1 for 3.25 seconds.
Action Taken When the DTC Sets
^ The TCM does not illuminate the malfunction indicator lamp (MIL).
^ The TCM commands maximum line pressure.
^ The TCM disables TAP Shift operation.
^ The TCM freezes transmission adaptive functions.
^ The TCM assumes D4 for shifting.
^ The TCM inhibits 3-2 downshifts when the vehicle speed is greater than 48 km/h (30 mph).
^ 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 and 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
