Circuit Description
The transmission fluid pressure (TFP) sensor is used to monitor the line pressure and feedback to the transmission control module (TCM) with an analog signal of 0-5 volts. The pressure sensor is fed with tier 2 feed fluid pressure and nominally ranges from 483-5861 kPa (70-850 psi). This diagnostic monitors the TFP circuit.
When the TCM detects a voltage signal that is excessively low, DTC P0842 sets. DTC P0842 is a type A 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 Line PC Solenoid DTCs P0960, P0961, or P0962. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The commanded line pressure is 2200 kPa (319 psi) or greater. |
Conditions for Setting the DTC
The TCM detects a measured line pressure value of 50 kPa (7 psi) or less for 9 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM commands a line pressure increase for all operating conditions |
| • | The TCM freezes main line pressure 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. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | 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
| • | To locate an intermittent problem, use the scan tool to monitor Line Pressure Actual with the engine running. Wiggle the wiring harness from the TCM to the transmission while watching for a change in the parameter. This may help locate the area where the fault in the wiring may lie. Also, check for poor terminal connections. |
| • | Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems. |
| • | A damaged module leadframe, damaged or missing differential thrust washer or excessive customer abuse can cause DTC P0842 to set. |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 |
Important:
Does the scan tool display a Line Pressure Actual reading less than the specified value? | 50 kPa (7 psi) | Go to Step 3 | Go to Intermittent Conditions in Engine Controls - 2.2L (L61) | ||||
3 |
Additional DTCs may set. Does the voltage measure near the specified value? | 5 V | Go to Step 4 | Go to Step 5 | ||||
4 | Connect a test light between the 5-volt reference circuit and the signal circuit of the TFP sensor. Does the scan tool display a Line Pressure Actual reading equal to or greater than the specified value? | 4500 kPa (653 psi) | Go to Step 7 | Go to Step 6 | ||||
5 | Test the 5-volt reference circuit of the TFP sensor for a short to ground, a short to the low reference circuit, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 | ||||
6 | Test the signal circuit of the TFP sensor for a short to ground, a short to the low reference circuit, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 | ||||
7 | Inspect for faulty connections at the transmission. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 | ||||
8 | Inspect for faulty connections at the TCM. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 | ||||
9 | Replace the TFP. The TFP is part of the control solenoid valve assembly. Refer to Control Valve Body Assembly Disassemble . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||
10 | Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, set-up and programming. Did you complete the replacement? | -- | Go to Step 11 | -- | ||||
11 | Perform the following procedure in order to verify the repair.
Has the test run and passed? | -- | Go to Step 12 | Go to Step 2 | ||||
12 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
