GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Cobalt 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0842 or P0843

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 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

    • No ISS DTCs P0716 or P0717.
    • No TCC performance DTCs P0741 or P0742.
    • No TCC PWM solenoid valve electrical DTCs P2763 or P2764.
    • The TCC is commanded OFF.
    • the TCC slip speed is greater than 100 RPM.
    • The vehicle speed is 16 km/h (10 mph) or more.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The transmission fluid temperature is between 20-130°C (68-266°F).
    • The engine torque is 50 N·m (37 lb ft) or more.

P0843

    • No ISS DTCs P0716 or P0717.
    • No TCC performance DTCs P0741 or P0742.
    • No TCC PWM solenoid valve electrical DTCs P2763 or P2764.
    • The TCC is commanded ON.
    • The TCC slip speed is -20 to +60 RPM.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The transmission fluid temperature is between 20-130°C (68-266°F).
    • The engine torque is 50 N·m (37 lb ft) or more.

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

    • DTC P0842 is a Type B DTC.
    • The TCM commands maximum line pressure.
    • The TCM commands the TCC ON at maximum capacity.
    • The TCM freezes transmission adaptive functions.
    • The TCM inhibits 4th gear if the transmission is in Hot Mode.

P0843

    • DTC P0843 is a Type B DTC.
    • The TCM forces the TCC OFF.
    • The TCM inhibits TCC engagement.
    • The TCM freezes transmission adaptive functions.
    • The TCM inhibits 4th gear if the transmission is in Hot Mode.

Conditions for Clearing the DTC

DTCs P0842 and P0843 are Type B DTCs.

Diagnostic Aids
    • Do not replace the torque converter for this condition. Refer to Torque Converter Diagnosis for other concerns.
    • Ensure the wiring harness is not stretched too tightly or other components are pressing on the AT inline 20-way connector body. Also inspect for proper clearance to any other components and wiring. Refer to Testing for Intermittent Conditions and Poor Connections .

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

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

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.
    2. ⇒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.
    3. ⇒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.
    4. ⇒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:
    5. • 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 .
⇒If any of the conditions are found, repair as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Transmission Fluid Pressure Manual Valve Position Switch Replacement
    •  Wiring Harness Replacement
    •  Control Module References for TCM replacement, setup, and reprogramming.