P0877

DTC P0877 or P0878

DTC Descriptor
This diagnostic procedure supports the following DTCs:
^ 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

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview





Typical Scan Tool Data





Circuit/System Description
The transmission fluid pressure (TFP) switch 4 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The TCM supplies 12 volts to the TFP Switch 4 on the TFP Switch 4 signal circuit; the TFP Switch 4 has an internal case ground. TFP Switch 4 is normally closed, Low. When oil pressure is present at the TFP Switch 4, the switch is Open, High. The normally low clutch pressure control (PC) solenoid 4 controls the transmission fluid to the 1-2-3-4 clutch. The TCM monitors the normally closed TFP Switch 4 signal circuit to determine the 1-2-3-4 clutch status.

Conditions for Running the DTC
^ No DTCs P0120, P0711, P0712, or P0713.
^ No DTCs P0965, P0966, P0967, P0968, P0969, P0970, or P0971.
^ No DTCs P0973, P0974, P0976, P0977, P2719, P2720, P2728, P2729, or P2730.
^ No DTCs P1825 or P1915.
^ Ignition voltage is between 11 - 15 volts.
^ The TFT is 20 - 150°C (68 - 302°F).

Conditions for Setting the DTC

DTC P0877
The TCM detects that the TFP Switch 4 signal voltage remains low, 0 volts when the 1-2-3-4 clutch is commanded ON, then the TCM sets DTC P0877.

DTC P0878
The TCM detects that the TFP Switch 4 signal voltage is high, 12 volts when the 1-2-3-4 clutch is commanded OFF, then the TCM sets DTC P0878.

Action Taken When the DTC Sets
^ DTCs P0877 and P0878 are Type C DTCs.
^ The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC
DTCs P0877 and P0878 are Type C DTCs.

Reference Information

Schematic Reference

Connector End View Reference
^ Automatic Transmission Inline 16-Way Connector End View
^ Automatic Transmission Internal Connector End Views

DTC Type Reference
^ Diagnostic Trouble Code (DTC) Type Definitions
^ Diagnostic Trouble Code (DTC) List/Type

Electrical Information Reference
^ Circuit Testing
^ Connector Repairs
^ Testing for Intermittent Conditions and Poor Connections
^ Wiring Repairs

Circuit/System Verification
If there are any other transmission related DTCs set, diagnose those DTCs first.

Circuit/System Testing
1. Ensure the TFT is near the temperature displayed in the Failure Records.
2. Start the engine and place the transmission range selector in D 6.
3. Observe the TFP Switch 4 parameter while commanding 4th gear and then commanding 5th gear with the scan tool. The TFP Switch 4 should transition from High in 4th gear to Low in 5th gear.
4. If the TFP Switch 4 parameter state does not change, perform the control solenoid (w/body and TCM) valve assembly inspection procedure.
5. If no concerns are found, replace the control solenoid (w/body and TCM) valve assembly.

Component Testing
Perform the control solenoid (w/body and TCM) valve assembly inspection procedure.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Control solenoid (w/body and TCM) valve assembly replacement.