6T70/6T75 - Automatic Transmission
DTC P0877 or P0878
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 P0877
- Transmission Fluid Pressure (TFP) Switch 4 Circuit Low Voltage
DTC P0878
- Transmission Fluid Pressure (TFP) Switch 4 Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The transmission fluid pressure (TFP) switch 4 is part of the control solenoid valve assembly which has no serviceable parts. The TCM supplies a signal circuit to the TFP switch 4. The TFP switch 4 has an internal case ground. TFP switch 4 is normally closed or LOW. When oil pressure is present at the TFP switch 4, the switch is open or HIGH. The normally LOW pressure control solenoid 5 controls pressure to the 1-2-3-4 clutch regulator valve. The TCM monitors the TFP switch 4 to determine the position of the 1-2-3-4 clutch regulator valve. When the 1-2-3-4 clutch is commanded OFF, pressure is present on the TFP switch 4. When the 1-2-3-4 clutch is commanded ON, the 1-2-3-4 clutch regulator valve moves and pressure to the TFP switch 4 is exhausted through the 1-2-3-4 clutch regulator valve.
Conditions for Running the DTC
P0877 or P0878
* No DTCs P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, P182E.
* The engine speed is 400 RPM or greater for 5 seconds.
* The engine speed is 550 RPM or greater.
* Ignition voltage is 8.6 volts or greater.
* The transmission fluid temperature (TFT) is 0-120°C (32-248°F).
Conditions for Setting the DTC
P0877
The TCM detects that the TFP switch 4 signal voltage remains LOW after the 1-2-3-4 clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 5 counts are accumulated.
P0878
The TCM detects that the TFP switch 4 signal voltage remains HIGH after the 1-2-3-4 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 8 counts are accumulated.
Action Taken When the DTC Sets
* DTCs P0877 and P0878 are Type C DTCs.
* The TCM freezes transmission adaptive functions for the 1-2-3-4 clutch.
Conditions for Clearing the DTC
DTCs P0877 and P0878 are Type C DTCs.
Diagnostic Aids
A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics Electrical Diagrams
Connector End View Reference
* Component Connector End Views Connector End Views By Name
* Inline Harness Connector End Views Connector Views
Description and Operation
* Transmission General Description Transmission General Description
* Electronic Component Description Electronic Component Description for control solenoid valve assembly
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
Special Tools
DT-47825-20 - Jumper Harness
Circuit/System Verification
1. If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Engine idling in Park with parking brake applied, and drive wheels chocked.
3. Monitor the TFP Switch 1, TFP Switch 3, TFP Switch 4, and TFP Switch 5 parameters with a scan tool.
4. Place the gear select lever in Park, Reverse, and Neutral range. Verify the TFP Switch 1, TFP Switch 3, TFP Switch 4, and TFP Switch 5 parameter states are correct for each range. 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 1, TFP Switch 3, TFP Switch 4, and TFP Switch 5 parameter states are correct for each range. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic.
6. 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. Ignition OFF. Remove the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement Service and Repair.
2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection Component Tests and General Diagnostics.
3. Place the control solenoid valve assembly on a clean work surface near the transmission assembly.
4. Connect DT-47825-20 - jumper harness between the vehicle wire harness electrical connector, and the control solenoid valve assembly electrical connector.
5. Ignition ON, verify with a scan tool that the TFP Switch 1, TFP Switch 3, TFP Switch 4, and TFP Switch 5 parameters changes states when gently pushing on each TFP switch with the eraser end of a pencil.
• If any TFP Switch parameter does not change states, replace the control solenoid valve assembly.
Repair Instructions
Note:
* Perform the Reset Transmission Adapts Programming and Relearning following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection Component Tests and General Diagnostics.
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for control solenoid valve assembly replacement, setup, or programming