VT25-E Automatic Transmission

VT25-E AUTOMATIC TRANSMISSION

DTC P0727
Circuit Description with VT25-E Automatic Transmission
Engine speed information is sent to the transmission control module (TCM) by the engine control module (ECM) through the GMLAN high-speed controller area network (HSCAN). A two-wire circuit is used to communicate data between the ECM and TCM, CAN H and CAN L. A fault in the HSCAN will not cause DTC P0727 to set by itself. If a communication fault occurs, other DTCs will set before P0727.

When the ECM sends the TCM an invalid engine speed, DTC P0727 sets. DTC P0727 is a type B DTC.

Conditions for Running the DTC
^ No HSCAN DTCs U2103, or U2105
^ The ignition voltage is 8 - 18 volts.

Conditions for Setting the DTC
The engine speed is invalid for 2.0 seconds.

Action Taken When the DTC Sets
^ The TCM requests the 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 moves the speed ratio towards a target ratio and then freezes ratio changes.
^ The TCM discontinues use of the closed loop ratio control algorithm. This causes the speed ratio to be defaulted and possibly not accurate. The resulting open loop control may or may not provide optimum ratio performance.
^ The TCM commands maximum pressure to the input clutch.
^ The TCM commands maximum line pressure.
^ The TCM calculates a default engine speed based on transmission input shaft speed.
^ The TCM freezes garage shift transmission adaptive functions.
^ 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 P0727 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.