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
Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
TCC Release Switch Signal
| P0842
| P0843
| P0843
| --
|
Scan Tool 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
| • | No ISS DTCs P0716 or P0717. |
| • | No TCC performance DTCs P0741 or P0742. |
| • | No TCC PWM solenoid valve electrical DTCs P2763 or P2764. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The transmission fluid temperature is between 20°C (68°F) and 130°C (266°F). |
| • | The engine torque is 50 N·m (37 lb ft) or more. |
DTC P0842
| • | The TCC is commanded OFF. |
| • | the TCC slip speed is greater than 80 RPM. |
| • | The vehicle speed is 16 km/h (10 mph) or more. |
DTC P0843
| • | The TCC is commanded ON. |
| • | The TCC slip speed is -20 to 60 RPM. |
Conditions for Setting the DTC
DTC P0842
The TCC release pressure switch is closed indicating release pressure not present for 10 seconds twice during the same ignition cycle.
DTC P0843
The TCC release pressure switch is open indication release pressure present for 6 seconds continuous twice during the same ignition cycle.
Action Taken When the DTC Sets
| • | DTCs P0842 and P0843 are Type B DTCs. |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM inhibits 4th gear if the transmission is in Hot Mode. |
DTC P0842
| • | The TCM commands maximum line pressure. |
| • | The TCM commands the TCC ON at maximum capacity. |
DTC P0843
| • | The TCM forces the TCC OFF. |
| • | The TCM inhibits TCC engagement. |
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 the Torque Converter Replacement Guide for other concerns. |
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
DTC Type Reference
Special Tools Required
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
- 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 the
J 35616
GM 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. |
- 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. |
- 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. |
- 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 #1 checkball damaged |
| • | The case cover or spacer plate gaskets improperly installed. Refer to
Case Cover Removal
in Transmission Unit Repair Manual. |
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
