HI there
This code is for a problem with the ecm relay. The main ecm relay isn't powering up the ecm properly or at all. What you should do is check all the fuses for the ecm and if they are all good, then change the ecm relay. Here is some more info
P0685 HONDA - Engine Control Module Power Relay Control Circuit Open Read more: https://www.autocodes.com/p0685_honda.html
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