6T30/6T40/6T45/6T50 - 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
- Clutch Pressure Control (PC) Solenoid 3 - Stuck Off
DTC P0797
- Clutch Pressure Control (PC) Solenoid 3 - Stuck On
Circuit/System Description
The clutch pressure control (PC) solenoid 3 is part of the control solenoid valve assembly which has no serviceable components. PC solenoid 3 regulates transmission fluid pressure to the R1/4-5-6 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 RPM signals from the automatic transmission input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.
Conditions for Running the DTC
P0796
* DTC P0121, P0122, P0123, P0716, P0717, P0722, P0723, or P182E is not set.
* Engine speed is greater than 500 RPM for 5 seconds.
* Output speed is greater than 650 RPM or accelerator pedal position is 1 percent or greater.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* The HSD is enabled.
* Throttle position signal is valid.
P0797
* 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.
* Throttle position signal is valid.
* Throttle position is greater than 8 percent.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* The transmission fluid temperature is 0°C (32°F) or greater.
* The HSD is enabled.
* The engine torque is between 50 Nm (36 lb ft) and 1 492 Nm (1,100 lb ft).
Conditions for Setting the DTC
P0796
The TCM detects an incorrect gear ratio when the 4-5-6 clutch is applied. This must occur 3 times.
P0797
The TCM detects an incorrect gear ratio when the 4-5-6 clutch is commanded OFF. This must occur 3 times.
Action Taken When the DTC Sets
P0796
* DTC P0796 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits TAP Up/TAP Down.
* The TCM inhibits manual up, manual down shifts with the shift selector.
* The TCM forces TCC off.
* The TCM enables torque management.
* The TCM limits the transmission to reverse and 3rd gear operation.
P0797
* DTC P0797 is a Type A DTC.
* The TCM commands maximum line pressure.
* The TCM inhibits TAP Up/TAP Down.
* Torque management is enabled.
* The TCM limits the transmission to reverse and 1st or 3rd gear operation.
Conditions for Clearing the DIC/DTC
DTCs P0796 and P0797 are Type A DTCs.
Diagnostic Aids
Before performing a road test, configure and setup the scan tool for snapshot mode. This allows you to monitor, display, and verify multiple transmission data parameters at one time, after the road test.
Reference Information
Schematic Reference
* Reverse (Reverse)
* Drive Range, First Gear Engine Braking (Drive Range, First Gear Engine Braking)
* Drive Range, First Gear (Drive Range, First Gear)
* Drive Range - Fourth Gear (Drive Range, Fourth Gear)
* Drive Range, Fifth Gear (Drive Range, Fifth Gear)
* Drive Range, Sixth Gear (Drive Range, Sixth Gear)
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)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) 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. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) , to verify correct fluid level and condition.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) , to dislodge debris and free up the valves.
4. Monitor the Transmission Fluid Pressure (TFP) switch 5 with a scan tool. Place the gear select lever in Park, Reverse, and Neutral range. Verify the TFP switch 5 parameter states are correct for Park, Reverse, and Neutral. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
5. Place the gear select lever in Drive range. Command the shift transmission with a scan tool through all forward ranges. Verify the TFP switch 5 parameter states are correct for all forward ranges. Refer to Transmission Fluid Pressure Switch Logic (Transmission Fluid Pressure Switch Logic).
6. Engine idling in Park, verify with a scan tool the Transmission ISS/OSS Supply Voltage test status parameter displays OK.
7. Engine idling in Park. Observe the Transmission ISS parameter on the scan tool, while varying the engine speed. The Transmission ISS parameter should vary with engine speed and not drop out.
8. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission OSS parameter on the scan tool. The Transmission OSS parameter should vary with the vehicle speed and not drop out.
Note: Perform a scan tool snapshot, during the road test.
9. Perform the Road Test (6T30/6T40/6T45/6T50 - Automatic Transmission). Verify the transmission operation performs as indicated in the road test instructions.
10. Review the scan tool snapshot data. Verify the following transmission data parameters display the correct values for each gear range.
* Transmission ISS
* Transmission OSS
* PC Solenoid 3
* TFP Switch 5
11. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Note: You must perform the Circuit/System Verification first.
1. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressures are within the range specified in the Line PC Solenoid Valve Pressure table. Refer to Solenoid Valve Pressure (Solenoid Valve Pressure).
• If not within the specified range, refer to Fluid Pressure High or Low (Fluid Pressure High or Low).
2. Ignition OFF, remove the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement (6T30/6T40/6T45/6T50 - Automatic Transmission).
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).
• If the control solenoid valve body does not pass the performance test, replace the control solenoid valve assembly.
4. Inspect for the following conditions and repair/replace as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Note: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
* Refer to Control Module References (Programming and Relearning) for control solenoid valve assembly replacement, setup, and programming.
* Perform the Service Fast Learn Adapts (Service Fast Learn Adapts) following all transmission related repairs.