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 P0842: Transmission Fluid Pressure (TFP) Switch 1 Circuit Low Voltage
DTC P0843: Transmission Fluid Pressure (TFP) Switch 1 Circuit High Voltage

### Circuit/System Description

The transmission fluid pressure (TFP) switch 1 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 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.

### 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

#### P0842

• | Without Start Test

• | Regular Test

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

- | The PC solenoid valve 2 hydraulic is 100 kPa or less for 0.45 second.

- | The pressure switch remain closed for 5.5 seconds.

#### P0843

• | Without Start Test

• | Regular Test

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

- | Engine running.

- | The PC solenoid valve 2 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 P0842 and P0843 are Type C DTCs.

• | The TCM freezes transmission adaptive functions.

### Conditions for Clearing the DTC

DTCs P0842 and P0843 are Type C DTCs.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component 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 observe the TFP Switch 1 parameter while moving the range selector lever from Park to Reverse. The TFP Switch 1 should transition from Hi in Park to Low in Reverse.

⇒ | If the TFP Switch 1 parameter does not change, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection.

⇒ | If no concerns are found, replace the control solenoid valve and TCM 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