Powertrain Diagnosis

This DTC indicates that the ECM received a message from the 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 CAN link to the BCM, which 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 when 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.

Diagnose any TCM related DTCs first.