DTC P0776 or P0777

Automatic Transmission - 10L80 MHS MQC | Diagnostic Information and Procedures | Document ID: 5224493 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0776 Transmission Control Solenoid Valve 2 Stuck Off DTC P0777 Transmission Control Solenoid Valve 2 Stuck On Diagnostic Fault Information

Note

DTC P0776 will set with a hydraulic/mechanical condition or high resistance in the circuit of the component Q77B without setting component/control circuit DTCs. DTC P0777 will set with a hydraulic/mechanical condition. The components are listed from the least to the most intrusive to service.

	Component	DTC	Condition
	Q77B Transmission Control Solenoid Valve 2	P0776, P0777	Binding, sticking or stuck component: Solenoid Valve Damaged or missing component: – Retaining Clip – Solenoid Valve
	1-2-8-9-10-Reverse Clutch Regulator Valve Valve Spring Valve Body Bore	P0776, P0777	Binding, sticking or stuck component: Valve Debris on the component. Damaged component: – Valve or Bore — Scored – Spring
	1-2-8-9-10-R Clutch Assembly — Oil Feed Circuit	P0776, P0777	Blocked or restricted component: Screen
	1-2-8-9-10-R Clutch Assembly	P0776, P0777	Blocked or restricted component: Fluid/oil passage
	© 2023 Gene	ral Motors. Al	Leaking component: l rights reserved.

Component	DTC	– Clutch Piston Condition
		– Clutch Housing – Gasket – O-Ring – Seal Binding, sticking or stuck component: Clutch Plates Damaged or worn component: – Clutch Plates – Clutch Piston – Clutch Housing

Circuit/System Description For an overview of the component/system, refer to: Park - Engine Running Reverse Neutral - Engine Running Drive Range, First Gear Drive Range, Second Gear Drive Range, Third Gear Drive Range, Fourth Gear Drive Range, Fifth Gear Drive Range, Sixth Gear Drive Range, Seventh Gear Drive Range, Eighth Gear Drive Range, Ninth Gear Drive Range, Tenth Gear Electronic Component Description The solenoid actuator controls fluid pressure by moving the clutch 1-2-8-9-10-R regulator valve that controls the fluid pressure to the 1-2-8-9-10-R clutch. Conditions for Running the DTC DTC P2534 = Not set DTCs related to the following system/component = Not Set – B14A Automatic Transmission Output Speed Sensor – B14C Automatic Transmission Input Speed Sensor – B14DA Automatic Transmission Intermediate Speed Sensor 1 – B14DB Automatic Transmission Intermediate Speed Sensor 2 – B303 Transmission Range Sensor – Transmission Control Solenoid Valves — Circuit DTCs Battery Voltage = Greater than 9 V Engine = Running High Side Driver 1, 2 = On Ignition and Start Signal = 9 to 32 V Ignition and Start Switch Signal = On Scan Tool Control Function = Not Activated Transmission Range = D, L or M One of the following conditions listed below is true: – Accelerator Pedal Position = Greater than 0.5% – Engine Speed = Greater than 1,000 RPM – Transmission Input Speed = Greater than 349 RPM – Transmission Output Shaft Speed = Greater than 35 RPM Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC P0776 Clutch 1-2-8-9-10-R = Not applied P0777 Clutch 1-2-8-9-10-R = Not released Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC — Additional actions taken: Autostart/Autostop = Disabled — If equipped Grade braking = Disabled Manual Shift Control = Disabled Neutral Idle Mode = Disabled Powertrain braking = Disabled Tap Up & Tap Down = Disabled TCC Control = Disabled Transmission Adaptive Pressure Control = Freeze current adapt values { P0776 } Transmission gear allowed = Reverse or Gear 7 { P0777 } Transmission gear allowed = Reverse or Gear 5 Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Diagnostic Aids High resistance in the circuits of the component Q77B may set DTC P0776 without setting control circuit DTC(s). Reference Information Component View Reference Transmission Solenoid Information DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

1. Verify the condition does not exist: Incorrect fluid level or condition » Refer to: Transmission Fluid Level and Condition Check ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
2. Ignition » On / Vehicle » In Service Mode
3. Verify DTC P0777 is not set. ⇒ If the DTC is set Refer to step 5 ⇓ If the DTC is not set

Note

For this test, the following scan tool parameter temperature needs to be between 20 and 80°C (68 and 176°F): Transmission Fluid Temperature The scan tool control function may turn off after 30 s.

4. Perform the scan tool control function: Transmission Control Solenoid Valve 2 » On — For greater than 2 s Verify the difference between the following parameters is less than 0.05 A: Transmission Control Solenoid Valve 2 Current Transmission Control Solenoid Valve 2 Current Command ⇒ If the difference is 0.25 A or greater Repair or replace the following as necessary: Circuit High Resistance High Resistance @ Q77 Transmission Control Solenoid Valve » Refer to: Transmission Solenoid Information ⇒ If the difference is between 0.05 and 0.25 A Perform the following steps:

Note

Determining the difference between the current parameters of the components will determine if a high resistance condition is present. This step compares the original component that set the DTC with a known good component (referred to as X) on this vehicle (same type) that does not have a DTC set. 4.1. Perform the scan tool control function: Transmission Control Solenoid Valve 2 » On — For greater than 2 s Monitor and record the difference between the following scan tool parameters: Transmission Control Solenoid Valve 2 Current Command & Transmission Control Solenoid Valve 2 Current 4.2. Perform the scan tool control function: Transmission Control Solenoid Valve X » On — For greater than 2 s @ A known good component on this vehicle (same type) » Refer to: Transmission Solenoid Information Monitor and record the difference between the following scan tool parameters: Transmission Control Solenoid Valve X Current Command & Transmission Control Solenoid Valve X Current 4.3. Verify the difference between the two recorded values is 0.05 A or less — The original component that set the DTC & A known good component on this vehicle (same type) ⇒ If the difference between the recorded values is greater than 0.05 A » Repair or replace the following as necessary: Circuit High Resistance High Resistance @ Q77 Transmission Control Solenoid Valve » Refer to: Transmission Solenoid Information ⇓ If the difference between the recorded values is 0.05 A or less 4.4. Refer to step 5 ⇓ If the difference is less than 0.05 A

5. Perform the following action: Clear the DTCs.
6. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Refer to: Road Test Verify that no DTC listed in the DTC Descriptor Category is set. ⇒ If any of the DTCs are set Refer to: Diagnostic Fault Information & Verify the conditions listed in the table do not exist ⇓ If none of the DTCs are set
7. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Control Valve Body Replacement For control module replacement, programming, and setup refer to: Control Module References Additional Procedures Transmission Service Fast Learn Procedure — Perform only when the component/system is serviced.