P0756
DTC P0756Diagnostic 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 Valve 2 Performance - Stuck Off
Circuit/System Description
The shift solenoid (SS) valve 2 is part of the control solenoid valve assembly, which has no serviceable components. The SS valve 2 is a normally closed (NC) solenoid valve and controls fluid to the clutch select valve 3. 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 moves and allows the metering ball to move away from the feed seat and against the exhaust seat, 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.
Conditions for Running the DTC
- DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
- The engine speed is 400 RPM or greater for 5.0 seconds.
- The high side driver is enabled.
- The ignition voltage is 8.6 volts or greater.
- The throttle position signal is valid.
- The transmission fluid temperature (TFT) is -7° C (19° F) or greater.
Conditions for Setting the DTC
- Commanded Gear is 1st locked.
- Gearbox Slip is 400 RPM or greater for 3.0 seconds.
- If above conditions exist, the TCM will command second range. If the gear ratio is between 2.7 and 3.0 for 1.0 second, the counter will increment. The DTC will set after 3 occurrences.
Action Taken When the DTC Sets
- DTC P0756 is a Type A DTC.
- The TCM inhibits Tap Up/Down function.
- The TCM inhibits manual shifting of forward gears.
- The TCM commands maximum line pressure.
- The TCM freezes transmission adaptive functions.
- The TCM limits the transmission to Reverse, 1st, and 3rd gear operation.
Conditions for Clearing the DTC
DTC P0756 is a Type A DTC.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
- Component Connector End Views
- Inline Harness Connector End Views
Description and Operation
Transmission General Description
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
Control Module References for scan tool information
Circuit/System Verification
1. Note
If other DTCs are set, diagnose those DTCs first.
Perform the Transmission Fluid Level and Condition Check to verify correct fluid level and condition. Component Tests and General Diagnostics
2. Note
Perform a scan tool snapshot, during the road test.
Perform the road test. Initial Inspection and Diagnostic Overview Verify the transmission operation performs as indicated, in the road test instructions.
3. 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 Valve 2
- Transmission Fluid Pressure Switch 1
- Transmission Fluid Pressure Switch 3
- Transmission Fluid Pressure Switch 4
- Transmission Fluid Pressure Switch 5
4. Record the Freeze Frame/Failure Records data. Clear the DTCs.
5. 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.
6. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the conditions for running fault codes (DTC). You may also operate the vehicle within the conditions you observe from the freeze frame/failure records. If the vehicle passes the circuit/system verification procedure, then stop. Do not perform the circuit/system test or component test as this may result in unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Perform the Line Pressure Check. Component Tests and General Diagnostics Check that the transmission's line pressure is within the range specified in the table Line PC-solenoid valve pressure. See Solenoid valve pressure.
2. If not within the specified ranges, refer to Fluid Pressure High or Low. Fluid Pressure High or Low
3. Remove control solenoid valve assembly Q8 with ignition OFF. See Replacing control solenoid valve assembly and transmission control module.
4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test. Component Tests and General Diagnostics Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid.
5. If the Q8 control solenoid valve assembly does not pass the performance test, replace the Q8 control solenoid valve assembly.
6. Listed in the table 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
Note
- Perform the Transmission Adaptive Values Learn following all transmission related repairs. Programming and Relearning
- Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection. Control Solenoid Valve and Transmission Control Module Assembly Inspection
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Control Valve Upper Body Assembly Cleaning and Inspection
- Control Module References for control solenoid valve assembly replacement, setup, or programming