P0873
DTC P0872 or P0873
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 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
Circuit/System Description
The Transmission Fluid Pressure Switch 3 is part of the control solenoid valve assembly which has no serviceable parts. The Transmission Control Module supplies a signal circuit to the Transmission Fluid Pressure Switch 3. The Transmission Fluid Pressure Switch 3 has an internal case ground. Transmission Fluid Pressure Switch 3 is normally closed or LOW. When oil pressure is present at the Transmission Fluid Pressure Switch 3, the switch is open or HIGH. The normally low clutch pressure control (PC) solenoid 4 controls pressure to the 2-6 clutch regulator valve. The Transmission Control Module monitors the Transmission Fluid Pressure 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 Transmission Fluid Pressure Switch 3. When the 2-6 clutch is commanded ON, the 2-6 clutch regulator valve moves and pressure is exhausted through the 2-6 clutch regulator valve.
Conditions for Running the DTC
P0872 or P0873
* TCM DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0751, P0742, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.
* Ignition voltage is between 8.6-32 V.
* The transmission fluid temperature (TFT) is -6.6°C (20°F).
* Engine speed is between 400-7500 RPM for 5 seconds.
* The high side driver is commanded ON.
Conditions for Setting the DTC
P0872
The Transmission Control Module detects that the Transmission Fluid Pressure Switch 3 signal voltage remains LOW after the 2-6 clutch transitions from a HIGH pressure state to a LOW pressure state. The Transmission Control Module counts each incident. The DTC sets when 10 counts are accumulated.
P0873
The Transmission Control Module detects that the Transmission Fluid Pressure Switch 3 signal voltage remains HIGH after the 2-6 clutch transitions from a LOW pressure state to a HIGH pressure state. The Transmission Control Module counts each incident. The DTC sets when 15 counts are accumulated.
Action Taken When the DTC Sets
* DTCs P0872 and P0873 are Type C DTCs.
* The Transmission Control Module freezes transmission adaptive functions.
Conditions for Clearing the DTC
DTCs P0872 and P0873 are Type C DTCs.
Diagnostic Aids
A Transmission Fluid Pressure Switch may malfunction due to normal debris in the transmission fluid causing a Transmission Fluid Pressure Switch DTC to intermittently set. This type of condition should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptive pressure 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 X101
Description and Operation
* Electronic Component Description Electronic Component Description
* Transmission General Description Transmission General Description
* Transmission Component and System Description Transmission Component and System Description
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-47825-10 - Jumper Harness
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
1. Engine idling in Park with parking brake applied, and drive wheels chocked.
2. Verify the scan tool parameters listed below display the correct values for each gear range while placing the gear select lever in Park, Reverse, and Neutral position. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic for the correct gear range states.
* Transmission Fluid Pressure Switch 1
* Transmission Fluid Pressure Switch 3
* Transmission Fluid Pressure Switch 4
* Transmission Fluid Pressure Switch 5
• If the switch logic is incorrect for a given gear range
Refer to Circuit/System Testing.
• If the switch logic is correct for all gear ranges
3. Place the gear select lever in Drive range.
4. Verify the scan tool parameters listed below display the correct values for each gear range while commanding the scan tool to Shift Transmission Gear through all forward ranges. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic for the correct gear range states.
* Transmission Fluid Pressure Switch 1
* Transmission Fluid Pressure Switch 3
* Transmission Fluid Pressure Switch 4
* Transmission Fluid Pressure Switch 5
• If the switch logic is incorrect for a given range
Refer to Circuit/System Testing.
• If the switch logic is correct for all gear ranges
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observe from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
7. All OK.
Circuit/System Testing
Note: You must perform the Circuit/System Verification first.
1. Ignition OFF. Remove the Q8 Control Solenoid Valve Assembly.
2. Verify and inspect the Q8 Control Solenoid Valve Assembly. The Q8 Control Solenoid Valve Assembly must be externally cleaned of all debris. Refer to 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-47825-10 - jumper harness between the vehicle wire harness electrical connector and the Q8 Control Solenoid Valve Assembly electrical connector. Ignition ON.
5. Verify the scan tool parameters listed below change states when gently pushing on each Transmission Fluid Pressure Switch with the eraser end of a pencil.
* Transmission Fluid Pressure Switch 1
* Transmission Fluid Pressure Switch 3
* Transmission Fluid Pressure Switch 4
* Transmission Fluid Pressure Switch 5
• If any Transmission Fluid Pressure Switch does not change states
Replace the Q8 Control Solenoid Valve Assembly.
• If all Transmission Fluid Pressure Switches change states
6. Verify the channel plate, spacer plate, and filter plate do not have a restricted or blocked orifice. Repair or replace as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Perform the Reset Transmission Adapts Reset Procedure following all transmission related repairs.
* Control Solenoid Valve and Transmission Control Module Assembly Replacement Service and Repair.
* Refer to Control Module References Control Module References for control solenoid valve assembly replacement, programming, and setup.