DTC P0756

/ 9-4x / 2011 / 4. Transmission / Automatic Transmission (6T70/6T75) / Fault diagnosis, diagnostic trouble codes / 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 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.

2.	Note Perform a scan tool snapshot, during the road test. Perform the road test . 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.	Register freeze frame/failure record data. Delete the diagnostic trouble codes.

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 you complete the steps described above, check the diagnostic trouble code is not reset by driving the vehicle according to the conditions for running diagnostic trouble codes (DTC). You can also drive the vehicle according to the conditions you see in 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 . Check that the transmission's line pressure is within the range specified in the table Line PC-solenoid valve pressure. Refer to Solenoid Valve Pressure .

2.	If not within the specified ranges, refer to 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 Test of the control solenoid valve assembly and the transmission control module's solenoid performance . Test all solenoid valves 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.

DTCs	Component	Condition
P0756	Upper Control Valve Body	• Clutch select valve 3 stuck off - debris, sediment, binding or scored bore • Bore plug - clutch select valve 3 - undersized bore plug causing a leak - plug should be a valve fit in the bore. • Check ball #3 - missing, damaged/malformed, Seat in the valve body damage/leaking.
P0756	Q8 Control Solenoid Valve Assembly	• Shift solenoid 2 not pressurizing - Stuck Off or leaking • Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal
P0756	Pump Assembly	Fluid pump vanes and fluid pump rotor broken
P0756	Pump Seal	Seal is torn or cut, causing a small leak that is overcome with enough speed and pump capacity.
P0756	Mechanical Diode	Broken or not capable of holding torque

Repair Instructions

Note
•	Perform the Resetting of the transmission's adaption after all transmission repairs.
•	Before replacing the TCM, perform the 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

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