P0843

VT25-E AUTOMATIC TRANSMISSION

DTC P0843





Circuit Description with VT25-E Automatic Transmission
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 high, DTC P0843 sets. DTC P0843 is a type A code.

Conditions for Running the DTC
^ No line PC solenoid DTCs P0960, P0961, P0962.
^ The ignition voltage is 8 - 18 volts.
^ The engine speed is greater than 500 RPM for 5 seconds.
^ The commanded line pressure is 4000 kPa (580 psi) or less.

Conditions for Setting the DTC
The TCM detects a measured line pressure value of 4500 kPa (653 psi) or greater for 20 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 P0843 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.
^ Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition.
^ Inspect the circuit wiring for an intermittent condition.