6T70 (M7W) - Automatic Transmission
DTC P0796 or P0797
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 P0796
- Pressure Control Solenoid Valve 3 Stuck Off
DTC P0797
- Pressure Control Solenoid Valve 3 Stuck On
Circuit/System Description
Clutch pressure control solenoid 3 is part of the control solenoid valve assembly, which has no serviceable components. Pressure Control solenoid 3 regulates transmission fluid pressure to the R1/4-5-6 clutch regulator valve which controls pressure to the low and reverse clutch and the 4-5-6 clutch. The transmission control module (TCM) calculates gear ratio based on the speed signals from the input speed shaft (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.
* 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.
* Transmission fluid temperature is -6.7°C (20°F) or greater.
* Engine torque is 20 Nm (15 lb ft) or greater when 1st gear is commanded-DTC P0797 only.
Conditions for Setting the DTC
P0796
The TCM has detected an incorrect gear ratio or neutral condition when the low and reverse clutch or the 4-5-6 clutch is commanded ON. This condition must occur 3 times.
P0797
The TCM has detected an incorrect gear ratio change when the low and reverse clutch or the 4-5-6 clutch is commanded OFF during a shift or when 4th gear ratio is detected in 1st gear. This condition must occur 3 times.
Action Taken When the DTC Sets
P0796
* DTC P0796 is a Type A DTC.
* TCM commands maximum line pressure.
* TCM freezes transmission adaptive functions.
* TCM inhibits Tap Up/Down function.
* TCM inhibits manual shifting of forward gears.
* TCM limits the transmission to Reverse, 1st, and 3rd gear operation.
* TCM inhibits auto grade braking.
* TCM inhibits neutral idle.
P0797
* DTC P0797 is a Type A DTC.
* TCM commands maximum line pressure.
* TCM freezes transmission adaptive functions.
* TCM inhibits Tap Up/Down function.
* TCM inhibits manual shifting of forward gears.
* TCM limits the transmission to Reverse and 4th gear operation.
* TCM inhibits neutral idle.
* TCM requests a reduced engine torque based on input speed.
* TCM inhibits auto grade braking.
Conditions for Clearing the DTC
DTCs P0796 and P0797 are Type A DTCs.
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
* Transmission Component and System Description Transmission Component and System Description
* Electronic Component Description Electronic Component Description
* Reverse Reverse
* Drive Range, First Gear Engine Braking Drive Range, First Gear Engine Braking
* Drive Range - Fourth Gear Drive Range - Fourth Gear
* Drive Range, Fifth Gear Drive Range, Fifth Gear
* Drive Range, Sixth Gear Drive Range, Sixth 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 is condition is correct
3. Ignition ON, clear the TCM DTCs with a scan tool.
4. Verify DTC P0796 or P0797 does not set while performing a road test. Refer to Road Test Road Test.
• If DTC P0796 or P0797 sets
Refer to Circuit/System Testing.
• If DTC P0796 or P0797 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.
P0796 or P0797 - Control Valve Upper Body Assembly
4-5-6 regulator valve stuck/sticking from debris, binding, damaged valve, or scored bore.
P0796 - Channel Plate and Spacer Plate
Channel Plate and spacer plate oil channels or orifices blocked by debris.
P0796 - Lower Control Valve Body Assembly
* Actuator feed limit circuit supply fluid to solenoid restricted or not available from debris, stuck limit valve, or sediment blockage.
* 4-5-6 clutch boost valve binding or a scored bore which can also cause harsh shifts.
* 4-5-6 clutch accumulator piston leaking, cracked, or broken.
P0796 or P0797 - Input Shaft Support
Input shaft support 3-5-R and 4-5-6 clutch fluid seal rings damaged, worn, or leaking.
P0796 or P0797 - Q8 Control Solenoid Valve Assembly
* Clutch pressure control solenoid valve 3 stuck ON or stuck OFF.
* Control solenoid filter plate assembly cracked, blocked, or damaged gasket seal.
P0796 - 4-5-6 Clutch Housing Assembly
* 4-5-6 clutch piston assembly damaged or leaking.
* 4-5-6 clutch inner/outer seal damaged.
* Dam pressure too high
P0796 - Automatic Transmission Case Cover
Blow off regulator ball stuck.
P0796 - Transmission Cooling/Lubrication
* Restriction/leak in oil to air cooler/radiator.
* Restricted/leaking/kinked/damaged transmission oil cooler lines.
* Restriction/leak in transmission fluid pump assembly.
P0796 - Torque Converter Assembly
Fluid pump or torque converter overstressed due to high temperature of fluid boiled out.
P0796 - 4-5-6 Reaction Carrier Hub Assembly
4-5-6 reaction carrier hub/shaft - broken hub weld.
P0796 - Automatic Transmission Fluid Filter Assembly
Oil filter or filter seal loose or damaged
P0796 - Automatic Transmission Fluid Pump
Pump fluid outlet seal assembly damaged/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.