GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 Yukon XL Denali 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0756

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 Descriptor

DTC P0756:  Shift Solenoid (SS) 2 Valve Performance - Stuck Off

Diagnostic Fault Information

The following fault table will help determine if a hydraulic circuit or an incorrect position or application of a component affects the transmission operation.

Component

Cause

DTCs

Lower Control Valve Body

Clutch select valve 3 stock - debris, sediment, binding or scored bore

P0756

1-2-3-4 and 3-5-R Clutch Housing Assembly

1-2-3-4 clutch backing plate retaining ring not seated, causing the piston to over-travel and cut 1-2-3-4 clutch piston seal

P0756

Control Solenoid (w/body and TCM) Valve Assembly

Clutch Pressure Control Solenoid 2:

    • Not exhausting - Stuck Off
    • Needle piston or armature pin binding
    • Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal
    • O-ring seals leaking

P0756

Center Support Assembly

Lube hole blocked, incorrectly drilled or omitted

P0756

Fluid Pump Cover Assembly

Fluid pump cover vanes and fluid pump rotor broken

P0756

Circuit/System Description

The shift solenoid (SS) valve 2 is part of the lower control valve body. The SS valve 2 is a normally closed (NC) solenoid valve and controls fluid to the clutch select valve 3- and related clutches. During this diagnostic test, intrusive actions are taken by the transmission control module (TCM) to test the SS valve 2 to see if the valve is stuck OFF. When in first gear engine braking, if first gear ratio is not achieved in a predetermined period of time, the TCM commands second gear and if second gear ratio is attained this indicates a stuck OFF SS valve 2 and the DTC will set.

Conditions for Running the DTC
    • First gear locked is commanded.
    • Attained gear slip is equal to or greater than 75 RPM for 2 seconds.

Conditions for Setting the DTC

The TCM detects second gear ratio is achieved.

Action Taken When the DTC Sets

DTC P0756 is a Type A DTC.

Conditions for Clearing the DTC

DTC P0756 is a Type A 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.

Reference Information

Schematic Reference

    •  Drive Range, First Gear Engine Braking
    •  Drive Range, First Gear

Description and Operation

Transmission Component and System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825 Control Solenoid Test Plate

Circuit/System Verification
  1. Perform the Transmission Fluid Check .
  2. Operate the vehicle in drive with the calculated throttle position greater than 15 percent to obtain 56 km/h (35 mph) 2 times.
    3. ⇒If the DTC resets, go to Circuit/System Testing.

Circuit/System Testing
  1. Perform the Line Pressure Check .
    2. ⇒If the pressure is out of specification correct that concern first.
  2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning and retest the DTC as outlined in the Circuit/System Verification steps.
    3. ⇒If the DTC resets, continue on with testing.
  3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
    4. ⇒If a concern is found, repair or replace the control solenoid (w/body and TCM) valve assembly.
  4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
    5. ⇒If the solenoid is found to be leaking or stuck OFF, replace the control solenoid (w/body and TCM) valve assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Replace the control solenoid (w/body and TCM) valve assembly. Refer to Control Module References for replacement, setup, or programming.
    • Perform the Service Fast Learn Adapts if internal transmission repairs are performed.