Monitor Description
WARNING: This page is about a different car, the 2019 Toyota Highlander, 2018 Toyota Highlander, and 2017 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
The hybrid vehicle control ECU assembly performs many diagnostic tests to verify proper operation of internal ECU systems. In one of these tests, the hybrid vehicle control ECU assembly checks the result of the ECM self-test. If the hybrid vehicle control ECU assembly detects a "Fail" from the ECM self-test, it will conclude that there is an internal malfunction in the ECM and will illuminate the MIL and store a DTC.