These type of Direct Trouble Codes (DTC)(s) can be hard to pin down. In the diagrams down below I have included for you a Honda factory diagnostic troubleshooting guide for pinpointing the problem that is causing your Malfunction Indicator Lamp (MIL), or "check engine" light to illuminate. Because it is turning on at freeway speeds, I would guess that it is emission related, but that might not be 100% accurate. The guide is a little lengthy, so please have patience and do not skip anything. It will require you to use a multi-meter, so if you are unfamiliar with how to use one I have included a link for you to go to below:
Please go through these guides and get back to us with what you are able to find out, please.
Images (Click to enlarge)
Wednesday, April 24th, 2019 AT 4:15 AM