Diagnostic Instructions

DTC Descriptors

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

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

Diagnostic Fault Information

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

Typical Scan Tool Data

TCC Release Pressure

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 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 powertrain control module (PCM) 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 PCM 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 10 seconds twice during the same ignition cycle.

P0843

The TCC release pressure switch is open indication release pressure present for 10 seconds continuous twice during the same ignition cycle.

Action Taken When the DTC Sets

P0842

P0843

Conditions for Clearing the DTC

DTC 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 Reference

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

Circuit/System Verification

Circuit/System Testing

Important: 

•	You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

•

When probing a terminal for testing procedures, it is imperative to use the proper test probe from the J 35616-D GM terminal test kit. Prior versions of the J 35616 GM terminal test kit do not contain the proper probes for testing TCM/ECM/PCM connectors. TCM/ECM/PCM harnesses use 0.64 mm (0.03 in) round terminals. The correct probe for this size terminal is the light blue J 35616-64B probe. ALL PREVIOUS J 35616-64 AND J 35616-64A PROBES SHOULD BE DISCARDED. The 1.00 mm (0.04 in) brown J 35616-6 probe is most widely mistaken for use with 0.64 mm (0.03 in) terminals. Use of the 1.00 mm (0.04 in) brown probe in a 0.64 mm (0.03 in) terminal will deform the terminal, likely resulting in an intermittent open condition.

1. Engine ON, vehicle in PARK. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display Yes.

⇒	If the TCC Release Pressure displays No, turn off the engine. Using the J 44257 main wiring harness connector remover, disconnect the automatic transmission inline 20-way connector.

2. Ignition ON, engine OFF. Observe the TCC Release Pressure parameter on the scan tool.

⇒

If the parameter displays Yes, install the J 44152 jumper harness on the automatic transmission 20-way pass-thru connector. Test the TCC release switch signal circuit for a short to ground between the jumper harness pin U and the TFP manual valve position switch terminal A. If the circuit tests good, replace the TFP manual position valve.

⇒

If the parameter displays No, install the J 44152 jumper harness on the engine side of the automatic transmission 20-way connector. Test the TCC release switch signal circuit for a short to ground between PCM X3 harness terminal 24 and the jumper harness connector terminal U. If the circuit tests good, replace the PCM.

3. 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. Using the J 44257 main wiring harness connector remover, disconnect the automatic transmission 20-way inline connector. Install the J 44152 jumper harness on the engine side of the automatic transmission 20-way connector. Using the J 35616 GM terminal test kit, jumper the TCC release switch circuit, jumper harness terminal U to ground. Turn ON the ignition with the engine OFF. Observe the TCC Release Pressure parameter on the scan tool.

⇒	If the TCC Release Switch parameter displays Yes, test the TCC release switch circuit for an open or short to voltage between the PCM X3 harness terminal 24 and the jumper harness terminal U. If the circuit tests good, replace the PCM.

⇒	If the parameter displays NO, install the J 44152 jumper harness on the automatic transmission 20-way pass-thru connector. Test the TCC release switch signal circuit for an open between the automatic transmission 20-way inline connector and the TFP manual valve position switch.

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 and Spacer Plate Assemble .

•	The case cover or spacer plate gaskets improperly installed--Refer to Case Cover Removal

5. If any of the conditions are found, repair as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.