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 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.
Conditions for Running the DTC
* DTCs P0121, P0122, P0123, P0716, P0717, P0722, P0723, or P182E are not set.
* Ignition voltage is 8.6 volts or greater.
* The engine speed is greater than 500 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 0°C (32°F) or greater.
Conditions for Setting the DTC
* Commanded gear is 1st locked.
* Transmission gearbox slip is 200 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 to Park, Reverse, Neutral, or 2nd 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 (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 (Programming and Relearning) 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, with parking brake applied and drive wheels chocked.
2. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level and condition.
Note: Perform a scan tool snapshot, during the road test.
3. Perform the Road Test (Road Test). Verify the transmission operation performs as indicated, in the road test instructions.
4. Review the scan tool snapshot transmission data parameters. Verify the engine and transmission data parameters display the correct values in all forward gear ranges:
* Engine Speed
* Transmission ISS
* Transmission OSS
* Vehicle Speed
* Shift Solenoid 2
* TFP Switches
5. Record the Freeze Frame/Failure Records data. Clear the DTCs.
6. Engine running, brakes applied, transmission gear shift selector in reverse. Shift to drive and accelerate to 56 km/h (35 mph) with calculated throttle position greater than 15 percent. Perform this test 5 consecutive times. The DTC should not set.
7. Operate the vehicle within the Condition for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressures are within the specified ranges.
• If not within the specified ranges, refer to Fluid Pressure High or Low (Fluid Pressure High or Low).
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 the Q8 control solenoid valve assembly does not pass the performance test, replace the Q8 control solenoid valve assembly.
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 Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
* Control Module References (Programming and Relearning) for control solenoid valve assembly replacement, setup, or programming.