P0756
DTC P0756
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0756
-
Shift Solenoid (SS) 2 Valve Performance - Stuck Off
Circuit/System Description
The shift solenoid (SS) 2 is part of the control solenoid valve assembly which has no serviceable parts. The control solenoid valve assembly is attached to the lower control valve body. The solenoid operates by the Transmission Control Module (TCM) opening or closing the ground circuit. With the solenoid circuit grounded (solenoid on), the internal plunger and metering ball block the exhaust fluid creating signal fluid pressure. The signal fluid acts against the clutch select valve 3 to overcome the valve spring force moving it to the apply position, allowing the shift. The TCM shifts the transmission by operating the solenoids in on/off combinations.
The SS 2 is commanded OFF in Reverse, and commanded ON in Park, Neutral, Drive 1 Engine braking, and Drive 1-6 gear ranges.
Conditions for Running the DTC
* No other ECM or TCM DTCs are set.
* Ignition voltage is 8.6 volts or greater.
* The engine speed is greater than 400 RPM.
* The engine run time is greater than 5 seconds.
* High Side Driver (HSD) 1 is enabled.
* Accelerator pedal position signal is valid
* The TCM must receive a valid torque signal from the ECM.
* Throttle position is 0.5 percent or greater.
* Transmission fluid temperature (TFT) is -6.6°C (20°F) or greater.
Conditions for Setting the DTC
* Commanded gear is 1st locked.
* Transmission gearbox slip is 400 RPM for 10 seconds.
* Transmission forces 2nd gear.
* Transmission has obtained a valid 2nd for 3 seconds.
Action Taken When the DTC Sets
* DTC P0756 is a Type A DTC.
* The TCM inhibits TAP function.
* The TCM inhibits TCC.
* The TCM freezes transmission adaptive functions.
* The TCM commands high line pressure.
* The transmission defaults Reverse gear, 1st gear, or 3rd gear.
Conditions for Clearing the DTC
DTC P0756 is a Type A DTC.
Diagnostic Aids
Before performing a road test, configure and setup the scan tool for snapshot mode. This will allow you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics Electrical Diagrams
Description and Operation
* Electronic Component Description Electronic Component Description
* Transmission Component and System Description Transmission Component and System Description
* Transmission General Description Transmission General Description
* Park - Engine Running Park - Engine Running
* Reverse Reverse
* Neutral - Engine Running Neutral - Engine Running
* Drive Range, First Gear Engine Braking First Gear Engine Braking
* Drive Range, First Gear First Gear
* Drive Range, Second Gear Second Gear
* Drive Range, Third Gear Third Gear
* Drive Range, Third Gear Default Third Gear Default
* Drive Range - Fourth Gear Fourth Gear
* Drive Range, Fifth Gear Fifth Gear
* Drive Range, Fifth Gear Default Fifth Gear Default
* Drive Range, Sixth Gear Sixth Gear
* Fluid Passages Fluid Passages
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
* DT-47825 - Control Solenoid Test Plate
* J 21867 - Pressure Gauge
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
Note:
If other DTCs are set, diagnose those DTCs first.
1. Engine idling in Park position, with parking brake applied and drive wheels chocked.
2. Verify transmission fluid level and condition. Refer to Transmission Fluid Level and Condition Check Transmission Fluid Level and Condition Check.
3. Ignition ON, clear the TCM DTCs.
4. Perform the Road Test Initial Inspection and Diagnostic Overview. Verify the transmission operation performs as indicated in the road test instructions and DTC P0756 did not set.
• If DTC P0756 is set
Refer to Circuit/System Testing below.
• If DTC P0756 did not set
5. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Perform the Line Pressure Check Line Pressure Check. Verify the transmission line pressures are within the specified ranges.
• If line pressures are not within the specified ranges
Refer to Fluid Pressure High or Low Fluid Pressure High or Low.
• If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement Service and Repair.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test. Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid valve.
• If a pressure change does not occur for each solenoid
Replace the Q8 control solenoid valve assembly.
• If a pressure change does occur for each solenoid
4. Listed in the chart below are conditions for each component that could set DTC P0756. Carefully inspect each component for that condition. Repair or replace as necessary.
Repair Instructions
* Perform the Reset Transmission Adapts Reset Procedure following all transmission related repairs.
* Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Control Module References Control Module References for control solenoid valve assembly replacement, setup, or programming.