For 1990-2009 cars

### 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 P0872: Transmission Fluid Pressure (TFP) Switch 3 Circuit Low Voltage
DTC P0873: Transmission Fluid Pressure (TFP) Switch 3 Circuit High Voltage

### 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

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 the 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 P182E or P1915.

• | The engine speed is 500 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

#### 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.

### Action Taken When the DTC Sets

• | DTCs P0872 and P0873 are type C DTCs.

• | The TCM freezes transmission adaptive functions.

### 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 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

#### Description and Operation

• | Transmission General Description

• | Electronic Component Description for control solenoid, w/body and TCM, valve assembly

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### 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. Perform the Control Solenoid Valve and Transmission Control Module Assembly Cleaning procedure to dislodge debris and free up valves.
3. Engine idling, parking brake applied, range selector in D, command the Shift Transmission with a scan tool to achieve 2nd gear.
4. 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

Note:

• | Perform the Service Fast Learn Adapts following all transmission related repairs.

• | Before replacing the TCM, perform the 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, w/body and TCM, valve assembly replacement, setup, or programming.