6T70 (M7W) - Automatic Transmission
DTC P0776 or P0777
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 Descriptors
DTC P0776
- Pressure Control Solenoid Valve 2 Stuck Off
DTC P0777
- Pressure Control Solenoid Valve 2 Stuck On
Circuit/System Description
Clutch 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-Reverse clutch regulator valve which controls pressure to the 3-5-Reverse clutch. The transmission control module (TCM) calculates gear ratio based on the speed signals from the input shaft speed (ISS) sensor and the output shaft speed (OSS) sensor. The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.
Conditions for Running the DTC
* DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
* Ignition voltage is greater than 8.5 V.
* Engine speed is 400-7,500 RPM for 5 s.
* Transmission fluid temperature is -6.7°C (20°F) or greater.
* Transmission output speed is 36 RPM or greater, or the accelerator pedal position is 0.5 % or greater.
* Throttle position signal is valid.
* High side driver is enabled.
* Engine torque is 20 Nm (15 lb ft) or greater - DTC P0777 only.
Conditions for Setting the DTC
P0776
TCM has detected an incorrect gear ratio or neutral condition when the 3-5-Reverse clutch is commanded ON. This condition must occur 3 times.
P0777
TCM has detected an incorrect gear ratio change when the 3-5-Reverse clutch is commanded OFF during a shift or when 3rd gear ratio is detected in 1st gear. This condition must occur 3 times.
Action Taken When the DTC Sets
P0776
* DTC P0776 is a Type A DTC.
* TCM commands maximum line pressure.
* TCM inhibits Tap Up/Down function.
* TCM freezes transmission adaptive functions.
* TCM inhibits manual shifting of forward gears.
* TCM limits the transmission to Reverse, 2nd, and 4th gear operation.
* TCM inhibits auto grade braking.
* TCM inhibits neutral idle.
P0777
* DTC P0777 is a Type A DTC.
* TCM commands maximum line pressure.
* TCM inhibits Tap Up/Down function.
* TCM inhibits manual shifting of forward gears.
* TCM freezes transmission adaptive functions.
* TCM limits the transmission to 3rd gear and Reverse operation.
* TCM inhibits auto grade braking.
* TCM inhibits neutral idle.
Conditions for Clearing the DTC
DTCs 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 6T70 (M7W) - Automatic Transmission
Connector End View Reference
* Component Connector End Views Sunshade - Left
* Inline Harness Connector End Views X110
Description and Operation
* Transmission General Description Transmission General Description
* Reverse Reverse
* Drive Range, Third Gear Drive Range, Third Gear
* Drive Range, Fifth Gear Drive Range, Fifth Gear
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
Warning: Refer to Parking Brake and Drive Wheels Warning Parking Brake and Drive Wheels Warning.
Note: If other DTCs are set, diagnose those DTCs first.
1. Engine idling, transmission in Park, parking brake applied, and drive wheels chocked.
2. Verify the transmission fluid level and condition is correct. Refer to Transmission Fluid Level and Condition Check 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
3. Ignition ON, clear the TCM DTCs with a scan tool.
4. Verify DTC P0776 or P0777 does not set while performing a road test. Refer to Road Test Road Test.
• If DTC P0776 or P0777 sets
Refer to Circuit/System Testing.
• If DTC P0776 or P0777 does not set
5. 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.
6. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
7. 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 Line Pressure Check and Solenoid Valve Pressure Solenoid Valve Pressure.
• If the pressures are not within range
Refer to Fluid Pressure High or Low 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 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 - Upper Control Valve Body Assembly
3-5-R regulator valve stuck/sticking - debris, binding, damaged valve, or scored bore.
DTC P0776 or P0777 - Lower Control Valve Body Assembly
* Actuator feed limit circuit supply fluid to solenoid restricted from debris, a stuck limit valve or sediment blockage.
* 3-5-R clutch boost valve - binding or scored bore - can cause harsh shifts.
DTC P0776 or P0777 - Q8 Control Solenoid Valve Assembly
* Clutch pressure control solenoid 2 stuck ON or stuck OFF.
* Control solenoid valve filter plate assembly, blocked or damaged gasket seal.
DTC P0776 - Channel Plate and Spacer Plate
Oil channels or orifices blocked by debris.
DTC P0776 or P0777 - Transmission Fluid Pump
* Fluid pump housing vanes/rotor/slide damaged/scored.
* Transmission pump fluid outlet seal assembly damaged/leaking.
DTC P0776 - Transmission Cooling/Lubrication
* Oil filter or filter seal loose, plugged, or damaged.
* Restriction/leak in oil to air cooler/radiator.
* Restricted/leaking/kinked/damaged transmission oil cooler lines.
* Restriction/leak in transmission fluid pump assembly.
DTC P0776 - Torque Converter Assembly
Torque converter overstressed due to high temperature, fluid boiled out.
DTC P0776 - 4-5-6 and 3-5-R Clutch Housing Assembly
* 3-5-R clutch backing plate retaining ring not seated or wave plate broken.
* 3-5-R piston seal torn, cut, or rolled.
* 4-5-6 and 3-5-R clutch housing assembly inner/outer seal damaged or dam pressure too high.
DTC P0776 or P0777 - Automatic Transmission Case Cover
Blow off regulator ball stuck.
DTC P0776 or P0777
3-5-R and 4-5-6 clutch fluid seal rings damaged, worn, or leaking.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repairs.
* Perform the Reset Transmission Adapts Reset Transmission Adapts following all transmission repairs.
* Control Module References Control Module References for control solenoid valve assembly replacement, programming, and setup.