Hi guys was wandering if u could shed some light on s little thing ive come across,
basically im driving volvo units and im getting the trailer abs light staying on on the warning display(orange) looked in the truck handbook and it says fault with trailer abs . what i need to no is it ok to drive like this how often does this happen, and what causes it , should i be defecting trailer or what??
Thanks guys
it may be a fault on the trailer but 9 times out of 10 it is simply because the trailer does not have abs on,
Are they old trailers?
A good indication of age is if it has the ISO abs socket on the bulkhead, its a newer one.
Try it on another trailer, maybe a newer one ?
Every time I’ve ‘defected’ a trailer for this, it has come back from the wksps as ‘no fault’ i.e. it’s just a compatability issue (new unit, older trailer) and is safe to use.
Me too, but I still note it down on the day’s defects as an “incompatibility fault”, to be on the safe side and cover my arse. 
NB. If it’s a RED light (rather than amber/yellow) then you’re risking a prohibition (PG9) if you take it out. RED means STOP whereas amber/yellow tends just to be advisory, whatever the symbol. 
It’s not a fault. VOLVO’s have always done this.
It’s like nice shiney wheel trim it’s added for no good reason at all, but simply because someone, in this case Volvo, likes it.
On the FL’s it was great as it gave you something do do on those long boring journeys, as by knocking the zb out of the dash you could get it to go out., or sometimes you could ,but only for a short while.
you not wrong about saying volvos do this often , the ones i have driven are x y and 53 plate and evry other 1 seems to have this light on.
On another point how would i no if there was a fault with the abs, today the trailer seemed to braking strage it was kind of trying to push the unit the unit was kinda of bunnyhopping under braking even at lowish speeds and when u press the brake pedal the light went out and when u realase it come back on.
I used to get this on my premium 
turned out to be a faulty lead.
One or two trailers still throw up the fault but disconnecting and then reconnecting lead seems to sort it
Untill it goes to red,don’t worry about it.It’s a compatability thing. They will still stop you.HONEST 
As a point ( or several) of interest…
Quite often it’s the ABS lead that’s causing the incompatibility. An ABS plug has 5 pins, whereas a new-fangled ABS/EBS lead has 7, the extra 2 pins carrying the EBS bit.
The sockets are designed so that you can plug a 5-pin plug into a 7-pin socket and vice-versa, presumably because they realised how long it would take for the newer version of the system to become standard.
If it’s a new unit on an old trailer, then you are probably putting a 7-pin plug into a 5-pin socket. The brakes still work perfectly well - ABS included - you just won’t have EBS because the trailer doesn’t have it. Changing the lead to one with a 5-pin plug will miraculously cure the “fault” on the dash.
If it’s the other way around (old unit/new trailer) then changing the lead won’t make a difference, because the trailer will still show as “incompatible” where the unit can’t do the EBS bit…but again, the ABS will still work and the rig is totally legal.
The only time a fault like this becomes illegal is if the little green light on the front of the trailer doesn’t do it’s stuff. IIRC, on most Haldex systems (the people who make the ABS/EBS bit) a green light will come on when you first start up, and then go off once you go over 10 or 15kph. This is the system’s inbuilt testing system, and if it doesn’t do that then you probably have a bigger problem, regardless of what the dash is saying - the whole compatibility thing confuses many tractor unit diagnostic setups.
The light/lights are usually very sensible placed on the bottom outside edge of the trailer, so it’s easy to keep an eye in your mirror and make sure it goes out when it’s supposed to…if the parts of the vehicle are compatible then their systems will work together and the yellow dashboard light will also go at when you reach the right speed, in harmony with the trailer check-light.
Most trailers with ABS will have an “idiot’s guide” to the green light system attached in the form of metal plates not far from the light itself. If they’re not there they’ve either been taken off or painted over. Personally I’d be a-whinging about that. 
If you want to be a total smartarse, a quick scout around the trailer will locate a small black box with a rubber cover (often embossed with “Haldex”, but not always). Carefully open this cover and you are now faced with the ABS onboard computer. Make a note of any codes or pictures shown (“spanner” is the one you want to worry about, but there are others) and ring whoever does your fitting and they should be able to confirm whether there is actually a problem or not. Note that on some of these computers you have to press a button to bring the codes up…and on the older ones that wipes them off the system, so making a note of what they are is vital if you need to get it sorted.
The Ministry are aware of these problems, and tend to go by the trailer’s testing system rather than the unit’s when establishing whether the rig is legal…so if the green light thing isn’t working as it should, don’t take it out!!!
Also, don’t be tempted to unplug the ABS lead to get shot of the light on the dash…get caught unplugged and it’s an instant prohibition which will not only go against the firm’s O-Licence, but may well put you out of a job when it’s so blatantly your fault.
Can someone please explain more about the greenlight on trailers ! when should they be on and when not .
Basically, you need to go by what the manufacturer’s plate at the front (or sometimes side) of the trailer tells you, as it depends on who built the system. Haldex ones seem to be most common, but there are others.
If you really want to go into detail about it, VOSA’s Guide to ABS Systems can be found HERE(It’s a .pdf ).
Details of all the different trailer light systems can be found on pages 16 - 20.
The rest of the document will tell you everything you could ever wish to know about ABS, and then some!!!
The ABS warning light often knocks the exhaust brake off with my Scania
After a few miles it might go out, exhaust returns, but often not…
Also have the same problem where I work but with DAF’s.
400 plus trailers, 60 plus units but two different units if connected to the same trailer, one might give orange ABS error, the other one does not.
Engineers agree its a compatibility problem
I just list in the vehicle log book the trailer I was connected to and the warning that is displayed.
I suppose at some point they might get round to analysing the fault, but as all the units are “53” and the trailers vary from brand new to very old its weird.
one thing that may help, when you are dropping or collecting a trailer, stop the engine and turn off the ignition.
This allows the unit’s computer to run its own checks when you are ready to drive off. it can cause compatibility problems if not, with some trailers.
It wont always cure it, but it can help.
and as Lucy said, Red means Stop in any language