That code is an ECU power relay. Could be a few things but might just be as easy as a fuse or a relay.

https://www.yourmechanic.com/articl...obd-ii-trouble-code-ecm-pcm-power-relay-circuit-malfunction-by-valerie-johnston

Sounds like exactly what you're seeing.

 

Needs some good diagnostics. From the info in your post I quickly think, all IMO:

Can not see a connection between the speed sensor and something mechanically wrong in the engine (although low oil and clicking sounds is certainly a separate mechanical issue).

Then you mention code P0685, which my quick google says its a ECM/PCM relay circuit code https://www.autocodes.com/p0685_honda.html. Normal engine operation certainly depends on the computer operating normally.

Gauges acting up; I can see the speedometer not working if the sensor failed, but the sensor is just a part of its circuit, there is also wiring, connectors, other parts hooked up, all need to be in contact and well. Check engine lights and key flashing (dunno the normal behavior of that "key" light, rarely notice it on my car. Anti-theft/security? that system is electrical).


You mention Canada, lots of snow? road salt (or is it too cold for salt over there?:surprise. I'm thinking electric problem is a possibility, maybe. A corroded and rusted ground? Harness connector rusted on the inside? You say "starter works fine" which indicates the engine is cranking over when u try to start it, but you also mention jump starting it.... Before, after?. Have u tried push staring it?

Electric problems can cause all sorts of randomness, random computer codes, and intermittent issues.

 

So what had happened was that I fried the ECU, the transmission sensor needed to change. I ended up with a cost of $1200 for the ECU, tranny sensor and the oil leak. But now I need a another tranny because mine just broke and its super super hard to find one in Toronto. Thanks for all the feedback I really appreciated it.