Hello, when I connect a trailer to my p38 after a minute or two it comes up with rear tail light fault. Thought is was the trailer at first but have tried three now all the same when I disconnect the trailer no issue the rear tail light. Any ideas?

You'll get a tail light fault if the BeCM sees either too low current draw (open circuit bulb) or too much current (short circuit bulb or holder). What lights do you have on the trailer? I once connected a 21W beacon to one sidelight circuit and after a short time it came up with the tail light fault warning. So if you have multiple lights running off the sidelight circuit (side markers?) it will draw too much current. It also cut power to that circuit so not only did the beacon go out but so did the tailights on that side.

Thankyou, my new one has side lights but the older ones where just standard trailer board ones. Would it be an idea to change from standard bulbs on the trailer to leds?

That will reduce the current draw so should stop it. It might be that your BeCM is a bit over sensitive and giving a false fail. I'd leave the indicator bulbs as standard tungsten so the trailer light on the dash still works. One of the trailers I often use has LED lights and there's no indication on the dash that the trailer indicators are working.

Thank will do