Hello , I need help with a problem with my 2004 honda accord coupe 2.4 DOHC.
I was driving it when the power electricity went off , it looked like power electrical shock, it was just for 1-2 seconds radio stopped working , lights on the dash went off too, and came back on again itself , and then check engine came on with code P0685 which means 1.open or short circuit condition or 2.Failed ECM
And there is one more thing ,I am not sure if there is something to do with this problem but when I drive it at night headlights blinks constantly ,every 2-3 minutes,it seems like electricity is not enough or so. What would recommend me to do ? does it seem like I need new ECM or I have to check wires?

 

I'm not sure what that code entails. It seems like you are losing power.

I would check all ends of both battery cables to make sure that they are not corroded and bolted on tightly.

Have the battery/alternator checked at an autoparts store.

 

According to my 03-06 Helm book...
P0685 = ECM/PCM Power Control Circuit / Internal Circuit Malfunction

I'm not real sure what that actually means in detail yet. I have the code list with me, but I last night I forgot to look this up in the actual Helm book. The 7th-gen seems to have more sophisticated control over the alternator, so maybe it's a problem with that system.

 

did u ever figure out the problem i have the same thing with my accord

 

My 2005 MDX check engine light came on the other day after I started the car just after refueling. I didn't have any symptoms before that point. Pulling the code (OBD port location was in front of my knee to the right of the steering column) showed P0685. After reading through this forum and several others, seems like the problem could be from:
1) bad battery
2) bad battery cables (corroded/loose)
3) bad ECM relays
4) bad ECM

I opened the hood and found that the positive (+) battery terminal was very corroded. Battery voltage showed about 12.4V. After cleaning the terminal (needed some fine sandpaper to get all of it off) and pulling both terminals out for about 15 minutes, I reconnected the terminals, started the car and put in my radio and nav codes. It's been 3 days and so far no more check engine light.