GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Yukon XL - 2WD 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0756 or P0757

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0756: 2-3 Shift Solenoid (SS) Valve Performance - No First or Second Gear

DTC P0757: 2-3 Shift Solenoid (SS) Valve Performance - No Third, Fourth or Fifth Gear

Circuit/System Description

The 2-3 shift solenoid (SS) valve controls the fluid flow acting on the 2-3 shift valves. The 2-3 SS valve is a normally-open exhaust valve that is used with the 1-2 SS valve, in order to allow 4 different shifting combinations.

Conditions for Running the DTC
    • No input speed sensor (ISS) DTCs P0716 or P0717.
    • No output speed sensor (OSS) DTCs P0722 or P0723.
    • No torque converter clutch (TCC) performance DTCs P0741 or P0742.
    • No shift solenoid electrical DTCs P0973, P0974, P0976, or P0977.
    • No internal mode switch (IMS) DTCs P1820, P1822, P1823, P1825, P1826 or P1915.
    • No torque converter clutch pulse width module (TCC PWM) DTCs P2763 or P2764.
    • No torque converter clutch enable DTCs P2769 or P2770.
    • The engine torque is greater than 50 N·m (37 lb ft).
    • The engine run time is greater than 5 seconds.
    • The engine is not in fuel cutoff.
    • The gear range is D4.
    • The throttle position is 8 percent or greater.
    • The input shaft speed is 50 RPM or greater.
    • The output shaft speed is 50 RPM or greater.
    • The transmission fluid temperature is 20-130°C (68-266°F).

Conditions for Setting the DTC

P0756

Both of the following conditions must occur twice during the same trip:

    • The TCM commands 1st gear and the resulting gear ratio is 0.65:1-0.72:1 for 2 seconds.
    • The TCM commands 2nd gear and the resulting gear ratio is 0.95:1 1.05:1 for 2 seconds.

P0757

Both of the following conditions must occur twice during the same trip:

    • The TCM commands 3rd gear and the resulting gear ratio is 1.54:1-1.71:1 for 2 seconds.
    • The TCM commands 4th gear and the resulting gear ratio is 2.91:1-3.21:1 for 2 seconds.

Action Taken When the DTC Sets

P0756

    • P0756 is a Type A DTC.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM inhibits 1st gear.

P0757

    • P0757 is a Type A DTC.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM inhibits 4th gear.

Conditions for Clearing the DTC

DTCs P0756 and P0757 are Type A DTCs.

Diagnostic Aids

The TCC fluid hydraulically applies the TCC, possibly causing an engine stall, under the following conditions:

    • The TCC is hydraulically stuck ON.
    • The parking brake is applied.
    • Any gear range is selected.
    • Contamination may cause the TCC apply valve to intermittently stick in the valve body.
    • Internal damage in the torque converter may cause no TCC apply.
    • Fluid contamination
       - Plugged fluid circuits
       - Restricted fluid circuits
    • Verify that the transmission meets the specifications in the Shift Speed table.
    • Refer to Shift Solenoid Valve State and Gear Ratio.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Information

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Transmission Control Module Scan Tool Information

Circuit/System Verification
  1. 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.
    2. ⇒If the transmission fluid is low or discolored, refer to Automatic Transmission Fluid and Filter Replacement.
  2. Operate the vehicle in Drive and ensure that the TCM commands all gears. The ratios should match the commanded gear for all gears. Refer to Shift Solenoid Valve State and Gear Ratio.
    3. ⇒If the gear ratios do not match the commanded gear, inspect the following and repair/replace as necessary:
    • Debris or chips in the actuator feed limit (AFL) oil passage
    • Debris or chips restricting oil flow in passage #29 of the case or through the spacer plate gasket into the valve body
    • A cracked 2-3 shift solenoid
    • A 2-3 shift valve which is stuck or hung up in the valve body bore
    • A 2-3 shuttle valve which is stuck or hung up in its bore
    • Damaged seals on the shift solenoid valves. Refer to Shift Solenoid Leak Test for further diagnosis.
  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.

Component Testing

Disconnect the wiring harness connector from the affected solenoid. Measure the resistance for the affected solenoid. The resistance should be between 19-31 ohms for the 2-3 SS.

⇒If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Shift Speed
    •  Automatic Transmission Fluid and Filter Replacement
    •  Shift Solenoid Valve State and Gear Ratio
    •  Shift Solenoid Leak Test