The ESP + SERV light on my Laguna II has been on for the past year or so. I grew to ignore it, although it was especially annoying when driving at night due to the glare. I've heard the ABS/ESP computer go costing hundreds, so choose to just do without it.
Well this weekend i've had a result and the ESP system is working as it should once more
I fitted new rear dics with bearings from Renault, as a rear wheel bearing had gone. You guessed it, the warning lights went. I understand the new discs came with a new sensor ring, but I cannot work out why if the ring was broken the ABS system would not also have a fault.
Hope this might be useful to others, I know the warning lights use to drive me