P0843
DTC P0842 or P0843
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provide an overview of each diagnostic category.
DTC Descriptors
DTC P0842
- Transmission Fluid Pressure (TFP) Sensor Circuit Low Voltage
DTC P0843
- Transmission Fluid Pressure (TFP) Sensor Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The torque converter clutch (TCC) release switch is part of the transmission fluid pressure (TFP) manual valve position switch. The TFP manual valve position switch is mounted to the transmission valve body. The TCC release switch is normally-closed. The switch signals the transmission control module (TCM) that the TCC is released. This is accomplished by torque converter release fluid pressure acting on the switch contact which opens the circuit. When the circuit voltage is high, the TCM recognizes that the TCC is no longer engaged.
Conditions for Running the DTC
P0842
* No ISS DTC P0716 or P0717.
* No TCC performance DTC P0741 or P0742.
* No TCC PWM solenoid valve electrical DTC P2763 or P2764.
* The engine speed is greater than 500 RPM for 5 seconds.
* The transmission fluid temperature (TFT) is between 20-130°C (68-266°F).
* The engine torque is 50 Nm (37 lb ft) or greater.
* The TCC is commanded OFF.
* the TCC slip speed is greater than 80 RPM.
* The vehicle speed is 16 km/h (10 mph) or greater.
P0843
* No ISS DTC P0716 or P0717.
* No TCC performance DTC P0741 or P0742.
* No TCC PWM solenoid valve electrical DTC P2763 or P2764.
* The engine speed is greater than 500 RPM for 5 seconds.
* The TFT is between 20-130°C (68-266°F).
* The engine torque is 50 Nm (37 lb ft) or greater.
* The TCC is commanded ON.
* The TCC slip speed is -20 to +60 RPM.
Conditions for Setting the DTC
P0842
The TCC release pressure switch is closed indicating release pressure not present for 10 seconds twice during the same ignition cycle.
P0843
The TCC release pressure switch is open indication release pressure present for 6 seconds continuous twice during the same ignition cycle.
Action Taken When the DTC Sets
* DTC P0842 and P0843 are type B DTCs.
* The TCM freezes transmission adaptive functions.
* The TCM inhibits 4th gear if the transmission is in Hot Mode.
P0842
* The TCM commands maximum line pressure.
* The TCM commands the TCC ON at maximum capacity.
P0843
* The TCM forces the TCC OFF.
* The TCM inhibits TCC engagement.
Conditions for Clearing the DTC
DTC P0842 and P0843 are type B DTCs.
Diagnostic Aids
* Do not replace the torque converter for this condition. Refer to Torque Converter Replacement Guide (Torque Converter Replacement Guide) for other concerns.
* Ensure the wiring harness is not stretched too tightly or other components are pressing on the automatic transmission inline 20-way connector body. Also inspect for proper clearance to any other components and wiring. Refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
* J 35616 GM Terminal Test Kit
* J 44152 Jumper Harness (20 pins)
Circuit/System Verification
Start the engine in PARK and observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display Yes. Drive the vehicle in D4 until the transmission shifts into 4th gear and the TCC is commanded ON. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display No.
Circuit/System Testing
1. Drive the vehicle in D4 until the transmission shifts into 4th gear and the TCC is commanded ON. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display No.
• If the TCC Release Pressure displays Yes, turn OFF the engine and disconnect the automatic transmission 20-way inline connector. Using the J 35616 GM terminal test kit, jumper the TCC release switch circuit at the engine harness side to ground. Turn ON the ignition with the engine OFF. If the TCC Release switch parameter displays Yes, test the TCC release switch circuit for an open between the TCM and the automatic transmission 20-way inline connector. If the parameter displays NO, test the TCC release switch signal circuit for an open between the automatic transmission 20-way inline connector and the TFP manual valve position switch.
2. Connect the automatic transmission 20-way inline connector. Start the engine and observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should indicate Yes.
• If the TCC Release Pressure displays No, disconnect the automatic transmission 20-way inline connector.
3. With the automatic transmission 20-way inline connector disconnected, observe the TCC Release Pressure parameter on the scan tool. The parameter should display Yes.
• If the parameter displays Yes, test the TCC release switch signal circuit for a short to ground between the automatic transmission 20-way inline connector and the TFP manual valve position switch. If the parameter displays No, test the TCC release switch signal circuit for a short to ground between the TCM and the automatic transmission 20-way inline connector.
4. Inspect for the following conditions that would cause TCC release pressure to be present when the TCC is applied:
* The turbine shaft O-ring seal leaking
* The turbine shaft oil seal rings missing or damaged
Refer to Torque Converter Assembly Removal (Overhaul).
* The TCC control valve damaged
Refer to Control Valve Body Disassemble (Overhaul).
* The #1 checkball damaged
* The spacer plate release exhaust blocked with debris
Refer to Control Valve Body and Spacer Plate Assemble (Overhaul).
* The case cover or spacer plate gaskets improperly installed
Refer to Case Cover Removal (Overhaul).
If any of the conditions are found, repair as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Transmission Fluid Pressure Manual Valve Position Switch Replacement (Service and Repair)
* Wiring Harness Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for TCM replacement, setup, and reprogramming