Just got back from the dealer and the P0400 code seems to be fixed. The dealer solution to replace the spaghetti tubes in the EGR system has, for the time being, fixed the check engine light. There is a check valve in one of the flexible lines (see photo) that deteriorated and caused the CEL. The tubes were clear and fee of contaminates and did not contribute to the failure code. If you are having an issue with the EGR, this could be the cause. A check valve is not listed anywhere in the manual. The dealer was not aware of its existence either. Only after more than an hour on the phone with Mitsubishi support was the potential solution identified.
GREEN MARKED TUBE TO VACUUM CONTROL VALVE contains the check valve but is not noted.
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