6T40/6T45 - Automatic Transmission
DTC P0842, P0843, P0872, P0873, P0877, P0878, P0989, or P0990
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 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
P0842 or P0843
The transmission fluid pressure (TFP) switch 1 is part of the control solenoid (w/body and TCM) valve assembly. The control solenoid (w/body and TCM) valve assembly has no seviceable parts. 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.
P0872 or P0873
The TFP switch 3 is part of the control solenoid (w/body and TCM) valve assembly. The control solenoid (w/body and TCM) valve assembly has no seviceable parts. The TCM supplies 12 volts to the TFP switch 3 on the TFP switch 3 signal circuit; the TFP switch 3 has an internal case ground. TFP switch 3 is normally closed, Low. When oil pressure is present at the TFP switch 3, the switch is Open, High. The normally low clutch PC solenoid 4 controls the transmission fluid to the 2-6 clutch. The TCM monitors the normally closed TFP switch 3 signal circuit to determine the 2-6 clutch status.
P0877 or P0878
The TFP switch 4 is part of the control solenoid (w/body and TCM) valve assembly. The control solenoid (w/body and TCM) valve assembly has no seviceable parts. The TCM supplies 12 volts to the TFP switch 4 on the TFP switch 4 signal circuit; the TFP switch 4 has an internal case ground. TFP switch 4 is normally closed, Low. When oil pressure is present at the TFP switch 4, the switch is open, high. The normally low clutch PC solenoid 5 controls the transmission fluid to the 1-2-3-4 clutch. The TCM monitors the normally closed TFP switch 4 signal circuit to determine the 1-2-3-4 clutch status.
P0989 or P0990
The TFP switch 5 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 5 on the TFP switch 5 signal circuit; the TFP switch 5 has an internal case ground. TFP switch 5 is normally closed, Low. When oil pressure is present at the TFP switch 5, the switch is open, high. The normally low clutch PC solenoid 3 controls the transmission fluid to the R1/4-5-6 clutch. The TCM monitors the normally closed TFP switch 5 signal circuit to determine the R1/4-5-6 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.
Diagnostic Aids
P0842
DTC P0842 detects that the C35R Pressure Switch is Exhausted when it should be Pressurized.
P0843
DTC P0843 detects that the C35R Pressure Switch is Pressurized when it should be Exhausted.
P0872
DTC P0872 detects that the CB26 Pressure Switch is Exhausted when it should be Pressurized.
P0873
DTC P0873 detects that the CB26 Pressure Switch is Pressurized when it should be Exhausted.
P0877
DTC P0877 detects that the C1234 Pressure Switch is Exhausted when it should be Pressurized.
P0878
DTC P0878 detects that the C1234 Pressure Switch is Pressurized when it should be Exhausted.
P0989
DTC P0989 detects that the CBR1/456 Pressure Switch is Exhausted when it should be Pressurized.
P0990
DTC P0990 detects that the CBR1/456 Pressure Switch is Pressurized when it should be Exhausted.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End 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
* 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
Circuit/System Verification
If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic System Check - Vehicle .
Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Engine idling, parking brake applied, range selector in Drive 6 (D), command the Shift Transmission special function with a scan tool to achieve 2nd gear.
2. Observe the suspect scan tool TFP Switch parameter while commanding the Shift Transmission special function 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, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection) .
• If no concerns are found, replace the control solenoid (w/body and TCM) valve assembly.
Repair Instructions
Perform the Diagnostic Repair Verification 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 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) .