Diagnostic Instructions

DTC Descriptors

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

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

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
TCC Release Switch Signal	P0842	P0843	P0843	--

Typical Scan Tool Data

Transmission Fluid Pressure (TFP) Switch Circuit Parameter Data

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
Operating Conditions: Engine running in Park, normal operating temperature Parameter Normal Range: Yes
TCC Release Pressure	No	Yes	Yes

Circuit/System Description

The torque converter clutch (TCC) release switch is part of the transmission fluid pressure (TFP) manual valve position switch. The TFP manual valve position switch is mounted to the transmission valve body. The TCC release switch is normally closed. The switch signals the transmission control module (TCM) that the TCC is released. This is accomplished by torque converter release fluid pressure acting on the switch contact which opens the circuit. When the circuit voltage is high, the TCM recognizes that the TCC is no longer engaged.

Conditions for Running the DTC

P0842

P0843

Conditions for Setting the DTC

P0842

The TCC release pressure switch is closed indicating release pressure not present for 8 seconds twice during the same ignition cycle.

P0843

The TCC release pressure switch is open indicating release pressure present for 6 seconds continuous twice during the same ignition cycle.

Action Taken When the DTC Sets

P0842

P0843

Conditions for Clearing the DTC

DTCs P0842 and P0843 are Type B DTCs.

Diagnostic Aids

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electronic Component Description for automatic transmission fluid pressure manual valve position switch assembly information

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 44152 Jumper Harness (20 pins)

Circuit/System Verification

Start the engine in PARK and observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display Yes. Drive the vehicle in D4 until the transmission shifts into 4th gear and the TCC is commanded ON. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display No.

Circuit/System Testing

1. Drive the vehicle in D4 until the transmission shifts into 4th gear and the TCC is commanded ON. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display No.

⇒	If the TCC Release Pressure displays Yes, turn OFF the engine and disconnect the AT 20-way inline connector. Using a terminal test kit , jumper the TCC release switch circuit at the engine harness side to ground. Turn ON the ignition with the engine OFF.

⇒	If the TCC Release switch parameter displays Yes, test the TCC release switch circuit for an open between the TCM and the AT 20-way inline connector.

⇒	If the parameter displays NO, test the TCC release switch signal circuit for an open between the AT 20-way inline connector and the TFP manual valve position switch.

2. Reconnect the AT 20-way inline connector. Start the engine and observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should indicate Yes.

⇒	If the TCC Release Pressure displays No, disconnect the AT 20-way inline connector.

3. With the AT 20-way inline connector disconnected, observe the TCC Release Pressure parameter on the scan tool. The parameter should display Yes.

⇒	If the parameter displays Yes, test the TCC release switch signal circuit for a short to ground between the AT 20-way inline connector and the TFP manual valve position switch.

⇒	If the parameter displays No, test the TCC release switch signal circuit for a short to ground between the TCM and the AT 20-way inline connector.

4. Inspect for the following conditions that would cause TCC release pressure to be present when the TCC is applied:

•	The turbine shaft O-ring seal leaking

•	The turbine shaft oil seal rings missing or damaged--refer to Torque Converter Assembly Removal .

•	The TCC control valve damaged--refer to Control Valve Body Disassemble .

•	The #1 checkball damaged

•	The spacer plate release exhaust blocked with debris--refer to Control Valve Body Assemble .

•	The case cover or spacer plate gaskets improperly installed--refer to Control Valve Body Cover Removal .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.