P1750

DTC P1750

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

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 Nm (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 (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Perform the Transmission Fluid Check (4T45-E Automatic Transaxle) 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.

• If the transmission fluid is low or discolored, refer to Automatic Transmission Fluid Filter and Seal Replacement (Service and Repair).

2. 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.

3. 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 (Verification Tests) after completing the diagnostic procedure.

* Transmission Fluid Check (4T45-E Automatic Transaxle)
* Symptoms - Automatic Transmission (- Symptoms - Automatic Transmission)
* Control Valve Body Disassemble (Overhaul)
* Side Cover/Gaskets, Disassemble, Assemble, Install (Overhaul)