P0843

DTC P0842 or P0843

DTC Descriptor
This diagnostic procedure supports the following DTCs:
^ DTC P0842 Transmission Fluid Pressure (TFP) Switch 1 Circuit Low Voltage
^ DTC P0843 Transmission Fluid Pressure (TFP) Switch 1 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 1 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 1 on the TFP Switch 1 signal circuit; the TFP Switch 1 has an internal case ground. TFP Switch 1 is normally closed, Low. When oil pressure is present at the TFP Switch 1, the switch is Open, High. The normally high clutch pressure control (PC) solenoid 2 controls the transmission fluid to the 3-5-R clutch. The TCM monitors the normally closed TFP Switch 1 signal circuit to determine the 3-5-R 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 P0842
The TCM detects that the TFP Switch 1 signal voltage remains low, 0 volts when the 3-5-R clutch is commanded ON.

DTC P0843
The TCM detects that the TFP Switch 1 signal voltage is high, 12 volts when the 3-5-R clutch is commanded OFF.

Action Taken When the DTC Sets
^ DTCs P0842 and P0843 are Type C DTCs.
^ The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC
DTCs P0842 and P0843 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 observe the TFP Switch 1 parameter while moving the range selector lever from Park to Reverse. The TFP Switch 1 should transition from Hi in Park to Low in Reverse.
3. If the TFP Switch 1 parameter does not change, perform the control solenoid (w/body and TCM) valve assembly inspection procedure.
4. If no concerns are found, replace the control solenoid valve and TCM 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.