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 P0877: Transmission Fluid Pressure (TFP) Switch 4 Circuit Low Voltage
DTC P0878: Transmission Fluid Pressure (TFP) Switch 4 Circuit High Voltage

### Circuit/System Description

The transmission fluid pressure (TFP) switch 4 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 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 pressure control (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.

### Conditions for Running the DTC

• | DTCs P0711, P0712 or P0713 are not set.

• | No DTCs P0965, P0966, P0967, P0968, P0969, P0970, or P0971

• | No DTCs P0973, P0974, P0976, P0977, P2719, P2720, P2728, P2729, or P2730.

• | No DTC P1825 or P1915.

• | DTC P2721 is not set.

• | The transmission fluid temperature (TFT) is between 20 and 150°C (68 and 302°F).

• | The engine speed is greater than or equal to 1,100 RPM.

### Conditions for Setting the DTC

#### P0877

• | Without Start Test

• | Regular Test:

- | The TCM does not turn off during the process.

- | Pressure control solenoid 5 hydraulic pressure is less than or equal to 100 kPa for 0.45 seconds.

- | The pressure switch remain closed for 5.5 seconds.

#### P0878

• | Without Start Test

• | Regular Test:

- | The TCM does not turn off during the process.

- | Engine running.

- | The PC solenoid valve 5 hydraulic is 600 kPa or greater for 1 second.

- | Keep the pressure switch OFF for 5.5 seconds.

### Action Taken When the DTC Sets

• | DTCs P0877 and P0878 are Type C DTCs.

• | The TCM freezes transmission adaptive functions.

### Conditions for Clearing the DTC

DTCs P0877 and P0878 are Type C DTCs.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

• | Automatic Transmission Inline 16-Way Connector End View

• | Automatic Transmission Internal Connector End Views

• | Automatic Transmission Related Connector End Views

#### DTC Type Reference

• | Diagnostic Trouble Code (DTC) Type Definitions

• | Diagnostic Trouble Code (DTC) List/Type

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Verification

If there are any other transmission related DTCs set, diagnose those DTCs first.

### Circuit/System Testing

1. Ensure the TFT is near the temperature displayed in the Failure Records.
2. Start the engine and place the transmission range selector in D6.
3. Observe the TFP switch 4 parameter while commanding 4th gear and then commanding 5th gear with the scan tool. The TFP Switch 4 should transition from High in 4th gear to Low in 5th gear.

⇒ | If the TFP switch 4 parameter state does not change, 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.

### Component Testing

Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Service Fast Learn Adapts

• | Control Module References for TCM replacement, setup, and programming