On the M273 V8 the guide gear of the timing chain wears out prematurely, because its material is soft. The chain runs on this wheel, so as it wears the position of the camshafts drifts relative to the crankshaft.

The maker's own bulletin gives fault codes 1200 and 1208 for this. What is typical is that the code comes straight back after being erased, on restart, so a freshly cleared fault memory does not hide it. The check engine light comes with it, along with uneven running and misfires.

It is not the mileage that decides but the engine number: the ones below 2739..30 088611 are the affected set, and engines built after that received a wheel made of stronger material.

For the repair the timing chain cover has to come off, but the cylinder heads do not have to be removed. The maker supplies a separate kit for this, number A272 030 03 13, which contains the guide wheel with its bearing, the chain tensioner, the oil pump, the solenoids and the seals. Removing and refitting the cover takes between 10.4 and 16.4 hours according to the maker's labour schedule, so the labour is what makes up the bill.

The same codes can more rarely be caused by a stretched timing chain as well. The symptoms of the two faults overlap, they can occur together and independently of each other, and because they are reached from the same place, both are worth looking at during one repair.