Heres a curious tale I thought I'd share with you all. We recently bought a Barchetta and one of the tail lights was out so I replaced both tail/ stop light bulbs with some fancy red LED bulbs. All seemed fine except the next time we went out in the car and put the headlights on, the ABS warning light came on and stayed on. It reset itself ok when the ignition was switched off but came back on if the headlights were used. The ABS itself was working ok cos I tested it on a wet road and it functioned fine. If we switched off the headlights the light would stay on and only went out when the ignition was switched off. I have now put ordinary bulbs in the tail lights and all is ok again!
What is going on?

are they LED type bulbes? I believe that the issue is that the current through the bulb is not enough for the 'bulb checking' wizzardry to recognise that its there. Thats the technical explanation anyway

Yes thats the ones. I heard a while back that the amber ones that can be used in indicators make the flasher unit go wild because its like the bulbs are missing, but I didn't imagine that the tail lights would have issues, at least not with the ABS

yeah its the same deal. If you look at the power rating of your old bulbs and the power rating of you new bulbs you'll see a huge difference. What you need to do is stick some resistors in there... to find the correct value just use the p=I^2 x R (substitute for R=V/I) rearrange with the values you know and you'll get the resistance you need... pop down to maplins and buy a few resistors... solder them in place and try again...

I think that formula resolves into something like R=P (in watts) x V^2 (in Volts). But my maths is a little dodgy sometimes.