Diagnostic Instructions

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

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
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

TFP Switches

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

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

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

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

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

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 .

⇒	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.