Tested car on anorther caravan all good and anorther car on my van no good
Factory fitted and all working
Fitted loads of towbars over years and yes know all about telling ecu or by pass
Had caravan nearly 10 yr and had this problem on van with last car but only just got round to sorting it
Cant get a wiring diagram so just going to have to trace back i think very complcated van for age