Circuit Description
The torque converter clutch (TCC) release switch is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The TFP manual valve position switch is attached to the control 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, thus opening the switch. When the voltage is high on the circuit, the TCM recognizes that the TCC is no longer engaged.
When the TCM determines that the TCC release switch is closed, indicating that the TCC is applied, and the TCC slip speed indicates that the TCC is not applied, then DTC P0842 sets. DTC P0842 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0842 Transmission Fluid Pressure (TFP) Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | No MAP DTCs P0107 or P0108. |
| • | No ISS DTCs P0716 or P0717. |
| • | No TCC performance DTCs P0741 or P0742. |
| • | No TCC electrical DTCs P2763 or P2764. |
| • | The engine is running for 5 seconds. |
| • | The transmission fluid temperature (TFT) is 20-130°C (68-266°F). |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The TCC is commanded OFF. |
| • | The TCC slip speed is greater than 100 RPM. |
| • | The vehicle speed is greater than 16 km/h (10 mph). |
Conditions for Setting the DTC
The TCC release switch is closed, release fluid pressure not present, for 8 seconds continuous, twice during the same trip.
Action Taken When the DTC Sets
| • | The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM commands maximum line pressure. |
| • | The TCM forces the TCC ON at maximum capacity. |
| • | The TCM inhibits 4th gear when in HOT mode. |
| • | The TCM freezes transmission adaptive functions. |
| • | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records. |
| • | The TCM stores DTC P0842 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The TCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Diagnostic Aids
| • | The default actions from DTC P0842 can cause DTC P0742 to falsely set. If DTC P0742 is also set, diagnose DTC P0842 first. |
| • | Ensure the wiring harness is not stretched too tightly or other components are pressing on the connector body. Also, inspect for proper clearance to any other components and wiring. Refer to Testing for Intermittent Conditions and Poor Connections . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear DTC Information function will erase the stored Freeze Frame and Failure Records from the TCM. Does the scan tool display Yes for TCC release pressure? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
Does the scan tool display Yes for TCC Release Pressure parameter? | Go to Step 4 | Go to Step 5 | |
4 | Test the TCC release switch signal circuit for a short to ground between the AT inline 20-way connector and the TFP manual valve position switch. Refer to Testing for Short to Ground . Did you find a condition? | Go to Step 6 | Go to Step 7 |
5 | Test the TCC release switch signal circuit for a short to ground between the TCM and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
6 | Replace the AT wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | Go to Step 9 | -- |
7 | Replace the TFP manual valve position switch. Refer to Transmission Fluid Pressure Manual Valve Position Switch Replacement . Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
9 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | Go to Step 10 | Go to Step 2 |
10 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
