I need a little help diagnosing a trailer brake issue. Basically, the brakes jerk and pull erratically when I apply the brakes. I get the same issue towing with both of my trucks, and a similar readout on the display -- my Ford w/ integrated controller gives a "faulty trailer wiring" or some such message, and my after-market inertia controller on my Chevy gives on "OC" readout, which is open circuit or something like that. So I don't think it is an issue with the truck wiring or controller -- I think it is something on the trailer side of the connector. Also, all lights work just fine on the trailer. Drums were adjusted on Saturday, but the issue did not go away.
Is there a separate ground for the brakes? Any ideas where I should look for clues?
Thanks in advance!
2008 Hornet Hideout 27B
2010 Chevy Suburban 1500 LT, Z71 package, 5.3/6A/3.42
2015 Ford F150 XLT Supercrew, 2.7 Ecoboost/6A/3.55 LS
Prior TVs:
2011 Ford F150 Ecoboost 3.5
2006 Chevy Silverado 2500HD Duramax LBZ
2005 Chevy Suburban 1500 4x4 LT, 5.3/4A/4.10