P0872
DTC P0872 or P0873Diagnostic 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 P0872
Transmission Fluid Pressure Switch 3 Circuit Low Voltage
DTC P0873
Transmission Fluid Pressure Switch 3 Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Transmission Fluid Pressure Switch 1
Transmission Fluid Pressure Switch 3
Transmission Fluid Pressure Switch 4
Transmission Fluid Pressure Switch 5
Circuit/System Description
The transmission fluid pressure (TFP) switch 3 is part of the control solenoid valve assembly, which has no serviceable components. The transmission control module (TCM) feeds a signal circuit to the TFP Switch 3. The TFP Switch 3 has an internal case ground connection. TFP Switch 3 is normally closed or LOW. When oil pressure is present at the TFP Switch 3, the switch is open or HIGH. The normally low clutch pressure control (PC) solenoid 4 controls pressure to the 2-6 reverse clutch regulator valve. The TCM monitors the TFP switch 3 to determine the position of the 2-6 clutch regulator valve. When the 2-6 clutch is commanded OFF, pressure is present on the TFP switch 3. When the 2-6 clutch is commanded ON, the 2-6 clutch regulator valve moves and pressure to the TFP switch 3 is exhausted through the 2-6 clutch regulator valve.
Conditions for Running the DTC
P0872 or P0873
- DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.
- The high side driver is enabled.
- The engine speed is 400 RPM or greater for 5 seconds.
- The engine speed is 550 RPM or greater.
- The ignition voltage is 8.6 volts or greater.
- The transmission fluid temperature (TFT) is -7 to +120° C (19-248° F).
Conditions for Setting the DTC
P0872
The TCM detects that the TFP switch 3 signal voltage remains LOW after the 2-6-clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 18 counts are accumulated.
P0873
The TCM detects that the TFP switch 3 signal voltage remains HIGH after the 2-6-clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 20 counts are accumulated.
Action Taken When the DTC Sets
- DTCs P0872 and P0873 are Type C DTCs.
- The TCM freezes transmission adaptive functions for the 2-6 clutch.
Conditions for Clearing the DTC
DTCs P0872 and P0873 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
Connector End View Reference
- Component Connector End Views
- Inline Harness Connector End Views
Description and Operation
- Transmission General Description
- Electronic Component Description for control solenoid valve assembly
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
DT-47825-20 Adapter Harness
For equivalent regional tools, refer to Special Tools.
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.
2. Engine idling in Park, with parking brake applied and drive wheels chocked.
3. Monitor the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters with a scan tool.
4. Place the gear select lever in Park, Reverse, and Neutral range. Verify the TFP Switch parameter states are correct for each range. Refer to 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 parameter states are correct for each range. Refer to Transmission Fluid Pressure Switch Logic.
6. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the conditions for running fault codes (DTC). You may also operate the vehicle within the conditions you observe from the freeze frame/failure records. If the vehicle passes the circuit/system verification procedure, then stop. Do not perform the circuit/system test or component test as this may result in unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Note
You must perform the Circuit/System Verification first.
Ignition off. Remove the Q8 control solenoid valve assembly.
2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection. Control Solenoid Valve and Transmission Control Module Assembly Inspection
3. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
4. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
5. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil.
6. If any TFP Switch parameter does not change states, replace the Q8 control solenoid valve assembly.
Repair Instructions
Note
- Perform the Transmission Adaptive Values Learn following all transmission related repairs. Programming and Relearning
- Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection. Control Solenoid Valve and Transmission Control Module Assembly Inspection
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for control solenoid valve assembly replacement, setup, or programming