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
• | No ISS DTC P0716 or P0717. |
• | No TCC performance DTC P0741 or P0742. |
• | The engine speed is greater than 500 RPM for 5 seconds. |
• | The transmission fluid temperature (TFT) is between 20-130°C (68-266°F). |
• | The engine torque is 30 N·m (22 lb ft) or greater. |
• | The TCC is commanded OFF. |
• | the TCC slip speed is greater than 80 RPM. |
• | The vehicle speed is 16 km/h (10 mph) or greater. |
P0843
• | No ISS DTC P0716 or P0717. |
• | No TCC performance DTC P0741 or P0742. |
• | The engine speed is greater than 500 RPM for 5 seconds. |
• | The TFT is between 20-130°C (68-266°F). |
• | The engine torque is greater than 30 N·m (22 lb ft). |
• | The TCC is commanded ON. |
• | The TCC slip speed is less than -20 RPM. |
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
• | DTC P0842 and P0843 are type B DTCs. |
• | The PCM freezes transmission adaptive functions. |
• | The PCM inhibits 4th gear if the transmission is in Hot Mode. |
P0842
• | DTC P0842 is a type B DTC. |
• | The PCM freezes transmission adaptive functions. |
• | The PCM inhibits 4th gear if the transmission is in Hot Mode. |
• | The PCM commands maximum line pressure. |
• | The PCM commands the TCC ON at maximum capacity. |
P0843
• | DTC P0843 is a type B DTC. |
• | The PCM freezes transmission adaptive functions. |
• | The PCM inhibits 4th gear if the transmission is in Hot Mode. |
• | The PCM forces the TCC OFF. |
• | The PCM inhibits TCC engagement. |
Conditions for Clearing the DTC
DTC P0842 and P0843 are type B DTCs.
Diagnostic Aids
• | DTC P0842 detects low voltage, a CLOSED TCC release switch, indicating the TCC is applied when the PCM is commanding the TCC off and TCC slip shows the TCC is OFF. |
• | DTC P0843 detects high voltage, an OPEN TCC release switch, indicating the TCC is not applied when the PCM is commanding the TCC ON and TCC slip shows the TCC is locked. |
• | Ensure the wiring harness is not stretched too tightly or other components are pressing on the automatic transmission 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 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
• | J 44257 Main Wiring Harness Connector Remover |
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. |
⇒ | If the TCC Release Pressure displays NO, go to 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, go to Circuit/System Testing. |
• | Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. |
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. |
- 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. |
- 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. |
- 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. |
- 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 |
- If any of the conditions are found, repair as necessary.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.