P1780

DTC P1780 (3.0L)

Circuit Description
To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by delaying the base ignition timing and notifying the TCM that the request has succeeded. If the ECM is unable to comply with the request, the ECM sends the TCM a message that the request has failed.

The torque reduction request is sent to the ECM through a communication network called the Controller Area Network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P1780 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P1780.

When the TCM receives a torque reduction failure message from the ECM, DTC P1780 sets. DTC P1780 is a type C DTC.

Conditions for Running the DTC
^ No other CAN errors are present.
^ The engine run time is greater than 5 seconds.

Conditions for Setting the DTC
The ECM notifies the TCM that a torque reduction request has failed for 2 seconds.

Action Taken When the DTC Sets
^ The TCM does not request the ECM to illuminate the Malfunction Indicator Lamp (MIL).
^ The TCM requests the ECM to illuminate the Service Vehicle Soon (SVS) lamp.
^ The TCM turns off the pressure control solenoid. When the pressure control solenoid is off, line pressure is at maximum and updates to the Transmission Adaptive Pressure (TAP) memory cells are discontinued.
^ 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 P1780 in TCM history.

Conditions for Clearing the SVS Lamp/DTC
^ The TCM clears the SVS lamp request when the condition no longer exists.
^ A scan tool can clear the SVS Lamp/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non emission related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

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DTC P1780 (3.0L)