6T70/6T75 - 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 2 Stuck Off
DTC P0777
- Pressure Control Solenoid 2 Stuck On
Circuit/System Description
The clutch pressure control solenoid 2 is part of the control solenoid valve assembly, which has no serviceable components. The pressure control solenoid 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
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.
* Ignition voltage is between 8.6-32.0 V.
* Engine speed is between 400-7500 RPM for 5.0 seconds.
* Transmission fluid temperature is -7°C (19°F) or greater.
* Transmission output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
* Throttle position signal is valid.
* High side driver is enabled.
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.
* Ignition voltage is between 8.6-32 V.
* Engine speed is between 400-7500 RPM for 5.0 seconds.
* Transmission Fluid Temperature is -7°C (19°F) or greater.
* Engine torque is 20 Nm (15 lb ft) or greater.
* Transmission output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
* Throttle position signal is valid.
* High side driver is enabled.
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 DIC/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 6T70/6T75 - Automatic Transmission
Connector End View Reference
* Component Connector End Views Sunshade - Left Front
* Inline Harness Connector End Views X110
Description and Operation
* Transmission General Description Transmission General Description
* Reverse Reverse
* Drive Range, Third Gear Third Gear
* Drive Range, Fifth Gear 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 in Park, with 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 6T70/6T75 - Automatic Transmission.
3. Ignition ON, engine OFF. Clear the TCM DTC information with a scan tool.
4. Perform the Road Test 6T70/6T75 - Automatic Transmission.
5. Verify DTC P0776 or P0777 did not set.
• If a DTC sets
Refer to Circuit/System Testing.
• If a DTC does not set
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.
7. Verify DTC P0776 or P0777 did not set.
• If a DTC sets
Refer to Circuit/System Testing.
• If a DTC did not set
8. All OK.
Circuit/System Testing
Note: You must perform the Circuit/System Verification first.
1. Verify the transmission line pressures are within the ranges specified in the Line PC Solenoid Valve Pressure table. Refer to Line Pressure Check Line Pressure Check and Solenoid Valve Pressure Solenoid Valve Pressure.
• If line pressures are not within the specified ranges
Refer to Fluid Pressure High or Low Fluid Pressure High or Low
• If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement Service and Repair.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test. Test all solenoids on the Q8 Control Solenoid Valve Assembly.
4. Verify a pressure change occurs for each solenoid valve.
• If a pressure change does not occur for each solenoid
Replace the Q8 Control Solenoid Valve Assembly.
• If a pressure change occurs for each solenoid
5. Verify the conditions listed below do not exist. Carefully inspect each component for that condition. Repair or replace as necessary.
* 3-5-R regulator valve stuck/sticking - debris, binding, damaged valve, or scored bore.
* 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.
* Clutch pressure control solenoid 2 stuck On or stuck Off.
* Control solenoid valve filter plate assembly, blocked or damaged gasket seal.
* Oil channels or orifices blocked by debris.
* Fluid pump housing vanes/rotor/slide damaged/scored.
* A/Trans pump fluid outlet seal assembly damaged/leaking.
* 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.
* Torque converter overstressed due to high temperature, fluid boiled out.
* 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.
* Blow off regulator ball stuck.
* 3-5-R and 4-5-6 clutch fluid seal rings damaged, worn, or leaking.
Repair Instructions
Note:
* Perform the Reset Transmission Adapts Reset Transmission Adapts following all transmission related repairs.
* 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 Verification Tests after completing the diagnostic procedure.
* Control Valve Lower Body and Upper Body Replacement Control Valve Lower Body and Upper Body Replacement
* Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal
* Control Module References Control Module References for control solenoid valve assembly replacement, setup, and programming