Automatic Transmission - 6T40/6T45
DTC P0842, P0843, P0872, P0873, P0877, P0878, P0989, or P0990
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0842
- Transmission Fluid Pressure (TFP) Switch 1 Circuit Low Voltage
DTC P0843
- Transmission Fluid Pressure (TFP) Switch 1 Circuit High Voltage
DTC P0872
- Transmission Fluid Pressure (TFP) Switch 3 Circuit Low Voltage
DTC P0873
- Transmission Fluid Pressure (TFP) Switch 3 Circuit High Voltage
DTC P0877
- Transmission Fluid Pressure (TFP) Switch 4 Circuit Low Voltage
DTC P0878
- Transmission Fluid Pressure (TFP) Switch 4 Circuit High Voltage
DTC P0989
- Transmission Fluid Pressure (TFP) Switch 5 Circuit Low Voltage
DTC P0990
- Transmission Fluid Pressure (TFP) Switch 5 Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The transmission fluid pressure (TFP) switch assembly is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The transmission control module (TCM) supplies 12 volts to each TFP switch via its respective signal circuit. The TFP switch assembly has an internal case ground. Each TFP switch is normally closed, Low. When oil pressure is present at the TFP switch, the switch is Open, High. The TCM monitors each normally closed TFP switch signal circuit to determine 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 P0977.
* No IMS DTCs P1825 or P1915.
* The engine speed is 1,100 RPM or greater.
* Ignition voltage is between 9.0 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 20 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 20 seconds or greater.
P0872
The TCM detects that the TFP switch 3 signal voltage remains low, 0 volts when the 2-6 clutch is commanded ON for 20 seconds or greater.
P0873
The TCM detects that the TFP switch 3 signal voltage is high, 12 volts when the 2-6 clutch is commanded OFF for 20 seconds or greater.
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 for 20 seconds or greater.
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 for 20 seconds or greater.
P0989
The TCM detects that the TFP Switch 5 signal voltage remains low, 0 volts when the low and reverse/4-5-6 clutch is commanded ON for 20 seconds or greater.
P0990
the TCM detects that the TFP Switch 5 signal voltage is high, 12 volts when the low and reverse/4-5-6 clutch is commanded OFF for 20 seconds or greater.
Action Taken When the DTC Sets
* DTCs P0842, P0843, P0872, P0873, P0877, P0878, P0989, and P0990 are Type C DTCs.
* The TCM freezes transmission adaptive functions.
Conditions for Clearing the DTC
DTCs P0842, P0843, P0872, P0873, P0877, P0878, P0989, and P0990 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)
* Range Reference (Range Reference)
* Shift Solenoid Valve State and Gear Ratio (6T40/6T45 - Automatic Transmission)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview).
2. Engine idling, parking brake applied, range selector in L (M), command the Shift Transmission with a scan tool to achieve 2nd gear.
3. Observe the suspect scan tool TFP Switch parameter while commanding the Shift Transmission with a scan tool to achieve 5th gear. Each TFP Switch parameter should toggle states (from High to Low or Low to High) between 2nd and 5th gear.
• If the specified parameter does not toggle, replace the control solenoid (w/body and TCM) valve assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Important: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
* Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.
* Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
* Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).