Hi everyone I am in desperate need of help.
I have a 2012 polo vivo 1.6 cls

My car epc popped up out of nowhere while on my way home from work.I had a diagnostic done which the fault code P0685 came up.
Ecm/ecu main relay open circuit.
Car goes into limp mode
The car has been to 3 mechanics all have failed to resolve the issue.
I have changed the throttle body,brake pedal switch the main relay 109 and the relay by the battery.All fuses checked.I did test for voltageat the relay and the number 30 wire to the computerbox..i have even changed the accelerator pedal and the computerbox.
I was fiddling around under the dash the car came right and ran for about 2 months and then the exact same fault came up again.i am out of solutions.

You may need an auto electrician to have a look at your car. Sounds like a wiring connection issue. Hope you get sorted

Had the same problem. Turned out to be power relay marked 109 has shaken almost all the way out of the fusebox. You can see it with a flashlight by removing the fusebox cover on the driver side of the dash and shining light through the hole.