I bought a '54 Volkswagen Touran 2.0TDi sport a month ago. I paid a high price because the car is as clean as a whistle inside and out and has done 100,000 miles. It has a full Volkswagen service history. I opted for no warranty, since in the past I found it wasn't worth the rag it was printed on.

A few days ago I had the car on some very gravelly roads, and in circumstances where the ESP should have kicked in, I noticed it wasn't. There was no flashing light on the dashboard and certainly no change in driving. I had a mate in the car who knows his Volkswagens, and to be honest, we were testing the ESP as I'd become suspicious as to why you couldn't turn the ESP off when pressing the button by the shifter. The ABS works fine, and apart from the ESP the brakes are spot on and the car drives superbly, handles well, etc. We whipped out a star drive and opened up the ESP switch console, and lo and behold, we found the switch unplugged. We plugged the switch back in, and hey-ho, the "ESP OFF" light is on all the time. Obviously I felt somewhat chagrined.

If the ESP unit is faulty (as we suspect), why is there no warning on the dashboard? Even when starting up, the ESP light does not come on. Is there any consequence of driving the car without the ESP on? I've heard that the diff can lock in the bends when it shouldn't, but I've not noticed any such behaviour at all, even when pushing the car to its limits. Also I've heard that an ESP light on indicates that the ABS as a whole is faulty, but the ABS definitely works. The car is booked in for a service so I'm sure Volkswagen will come up with a fault, I just wanted some background info before I get talked into replacing the ESP unit.