Chevrolet Trax: DTC P0776 OR P0777

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 Descriptors

NOTE: The DTCs listed below set due to a transmission hydraulic/mechanical condition. Perform the Circuit/System Verification and Circuit/System Testing to identify the cause.

DTC P0776

Pressure Control Solenoid Valve 2 Stuck Off - Transmission Hydraulic/Mechanical Performance

DTC P0777

Pressure Control Solenoid Valve 2 Stuck On - Transmission Hydraulic/Mechanical Performance

Circuit/System Description

Pressure control solenoid valve 2 is part of the control solenoid valve assembly, which has no serviceable components. Pressure control solenoid valve 2 regulates transmission fluid pressure to the 3-5-R regulator valve, which controls pressure to the 3-5-R clutch. The transmission control module (TCM) calculates gear ratio based on the speed signals from the input shaft speed sensor and the output shaft speed sensor. The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.

Conditions for Running the DTC

P0776

• 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.
• Engine speed is 400-7,500 RPM for 5 s.
• Ignition voltage is 9-32 V.
• Transmission fluid temperature is -6.7ºC (20ºF) or greater.
• Transmission output speed is 100 RPM or greater, or the throttle position is 0.5% or greater.
• Throttle position signal is valid.
• High side driver is enabled.
• Commanded range is reverse, 3rd gear or 5th gear.
• DTC runs continuously when the above conditions are met.

P0777

• 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.
• Engine speed is 400-7,500 RPM for 5 s.
• Ignition voltage is 9-32 V.
• Transmission fluid temperature is -6.7ºC (20ºF) or greater.
• Transmission output shaft speed is 100 RPM or greater, or the throttle position is 0.5% or greater.
• Throttle position signal is valid.
• High side driver is enabled.
• Throttle position is 10% or greater and the engine torque is 45 N.m (33 lb ft) or greater.
• DTC runs continuously during shift when the 3-5-R clutch is commanded OFF, until commanded range is attained.

Conditions for Setting the DTC

P0776 - Condition 1

• Commanded gear is 3rd.
• Gearbox slip of 400 RPM or greater is detected for 2.5 s.
• TCM commands 4th gear if the above conditions exist and detects a gear ratio of 1.37-1.52 for 3 s.
• Conditions listed above have to occur 2 times.

P0776 - Condition 2

• Commanded gear is 5th.
• Gearbox slip of 400 RPM or greater is detected for 3 s.
• TCM commands 6th gear if the above conditions exist and detects 6th gear ratio for 3.5 s.
• Conditions listed above have to occur 3 times.

P0777

• The TCM detects an incorrect off-going clutch gear ratio, or tie-up, when the 3-5-R clutch is commanded OFF for 1 s.
• The transmission input shaft speed is 400 RPM or less from the anticipated input shaft speed.
• The conditions listed above must occur 3 times.

Action Taken When the DTC Sets

P0776

• P0776 is a Type A DTC.
• TCM commands maximum line pressure.
• TCM freezes transmission adaptive functions.
• TCM inhibits TAP Up/TAP Down function.
• TCM inhibits manual shifting of forward gears.
• TCM inhibits powertrain braking.
• TCM inhibits auto grade braking.
• TCM inhibits neutral idle.
• TCM commands 2nd gear if the transmission is in a forward gear and the output speed is less than 700 RPM.
• TCM commands neutral if the output speed is 700 RPM or greater.

P0777

• P0777 is a Type A DTC.
• TCM commands maximum line pressure.
• TCM limits the transmission to reverse and 3rd gear.
• TCM freezes transmission adaptive functions.
• TCM inhibits TAP Up/TAP Down function.
• TCM inhibits manual shifting of forward gears.
• TCM inhibits neutral idle.
• TCM inhibits powertrain braking.
• TCM inhibits auto grade braking.

Conditions for Clearing the DTC

P0776 and P0777 are Type A DTCs.

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 (Encore, MH8 or MHB) , Automatic Transmission Controls Schematics (Trax, MH8 or MHB)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

• Inline Harness Connector End Views (Encore) , Inline Harness Connector End Views (Trax)

Description and Operation

• Drive Range, Third Gear (Gen 2/Hybrid)
• Drive Range - Fourth Gear (Gen 2/Hybrid)
• Drive Range, Fifth Gear (Gen 2/Hybrid)
• Electronic Component Description
• Transmission Component and System Description
• Transmission General Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (LUV) , Powertrain Diagnostic Trouble Code (DTC) Type Definitions (2H0)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

WARNING: Refer to Parking Brake and Drive Wheels Warning .

NOTE: If other DTCs are set, diagnose those DTCs first.

1. Ignition ON.
2. Verify DTC P0716, P0717, P0722, P0723, P077C, P077D, P07BF, or P07C0 was not set by reviewing the scan tool Freeze Frame/Failure Records data.

If any of the DTCs were set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

If none of the DTCs were set

3. Engine idling, transmission in Park, with parking brake applied and drive wheels chocked.
4. Verify the transmission fluid level and condition is correct. Refer to Transmission Fluid Level and Condition Check.

If the transmission fluid level and condition is not correct

Repair as necessary.

If the transmission fluid level and condition is correct

5. Ignition ON, clear the TCM DTCs with a scan tool.
6. Verify DTC P0776 or P0777 does not set while performing a road test. Refer to Road Test.

If DTC P0776 or P0777 sets

Refer to Circuit/System Testing.

If DTC P0776 or P0777 does not set

7. 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.
8. Verify the DTC does not set.

If the DTC sets

Refer to Circuit/System Testing.

If the DTC does not set

9. All OK.

Circuit/System Testing

NOTE: You must perform the Circuit/System Verification first.

1. Engine idling at the normal operating temperature.
2. Verify the transmission line pressures are within the specified range. Refer to Line Pressure Check, and Solenoid Valve Pressure (Gen 2) .

If the pressures are not within range

Refer to Fluid Pressure High or Low.

If the pressures are within range

3. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
4. Verify the pressure changes for all solenoids when performing the solenoid test. Refer to Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test.

If the pressure does not change

Replace the Q8 Control Solenoid Valve Assembly.

If the pressure changes

5. Verify the mechanical conditions listed below do not exist. Repair or replace as necessary.

DTC P0776 or P0777 - Control Valve Body Assembly

• Actuator feed limit circuit supply fluid to solenoids restricted or not available - debris or sediment blockage.
• 3-5-R Regulator Valve stuck/sticking - debris, binding, damaged valve, or scored bore.
• Control valve body ball check valve not seating correctly - debris.

DTC P0776 - 3-5-R and 4-5-6 Clutch Housing Assembly

3-5-R clutch backing plate retaining ring not seated, causing clutch pack over-travel.

DTC P0776 or P0777 - Torque Converter (w/Fluid Pump) Housing Assembly

Fluid pump housing/gear damaged/scored

DTC P0776 - Channel Plate and Spacer Plate

Oil channels or orifices blocked by debris.

DTC P0776 or P0777 - Q8 Control Solenoid Valve Assembly

• Clutch Pressure Control Solenoid 2 stuck ON/OFF.
• O-ring seals leaking.
• Valve body filter plate assembly cracked, blocked, or damaged gasket seal.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Perform the Transmission Adaptive Values Learn following all transmission repairs
• Control Module References - for Control Solenoid Valve Assembly replacement, programming and setup

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