Powertrain Diagnosis

P1780- TCM REQUESTED MIL ILLUMINATION
This DTC indicates that the engine control module (ECM) received a message from the transmission control module (TCM) to turn On the MIL (SERVICE ENGINE SOON) telltale due to a transmission related OBD II failure. The ECM will send a message via the controller area network (CAN) link to the body control module (BCM) who will send a message over the Class II link to the I/P cluster to turn On the MIL.

DTC PARAMETERS
DTC P1780 will set if the ECM received a MIL request message from the TCM over the CAN link.

P1780 is a type B DTC

DIAGNOSTIC AIDS
DTC P1780 does not indicate a fault with the CAN link circuit.

DTC P1780 does not indicate a fault with the ECM. Diagnose any TCM related DTCs first.