Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0842: Transmission Fluid Pressure (TFP) Switch 1 Circuit Low VoltageDTC P0843: Transmission Fluid Pressure (TFP) Switch 1 Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
TFP Switch 1 Signal | P0842 | P0843 | P0843 | -- |
TFP Switch 3 Signal | P0872 | P0873 | P0873 | -- |
TFP Switch 4 Signal | P0877 | P0878 | P0878 | -- |
TFP Switch 5 Signal | P0989 | P0990 | P0990 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running, normal operating temperature Parameter Normal Range: 12 Volts = Hi, 0 Volts = Low | |||
TFP Switch 1 | Low | Hi | Hi |
TFP Switch 3 | Low | Hi | Hi |
TFP Switch 4 | Low | Hi | Hi |
TFP Switch 5 | Low | Hi | Hi |
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 TFT DTCs P0711, P0712, or P0713. |
| • | No pressure control solenoid electrical DTCs P0965, P0966, P0967, P0969, P0970, P0971, P2719, P2720, P2721, P2728, P2729, or P2730. |
| • | No shift solenoid electrical DTCs P0973, P0974, P0976, or P09770. |
| • | No IMS DTCs P1825 or P1915. |
| • | The engine speed is 1,100 RPM or greater. |
| • | Ignition voltage is between 8.6 volts and 19.0 volts. |
| • | The transmission fluid temperature (TFT) is 20-150°C (68-302°F). |
Conditions for Setting the 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 for 5.5 seconds or greater.
P0843
The TCM detects that the TFP switch 1 signal voltage is high, 12 volts when the 3-5-R clutch is commanded OFF for 5.5 seconds or greater.
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
Automatic Transmission Controls Schematics
Connector End View Reference
DTC Type Reference
Electrical Information Reference
Circuit/System Verification
If there are any other transmission related DTCs set, diagnose those DTCs first.
Circuit/System Testing
- Ensure the TFT is near the temperature displayed in the Failure Records.
- 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.
| ⇒ | If the TFP Switch 1 parameter does not change, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection . |
| ⇒ | If no concerns are found, replace the control solenoid valve and TCM assembly. |
Component Testing
Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.
- Perform the Service Fast Learn Adapts .
