At a cold start a brief, metallic rattle comes from the front of the engine, and it has two causes. With the engine stopped the oil drains out of the passages of the timing chain tensioner, so at start-up the tensioner begins dry, and until the pressure builds back up the chain rattles. The camshaft adjuster rattles for the same reason.

The rattle lasts one to two seconds and then goes quiet, and that length is exactly what matters. A rattle of a couple of seconds points to the tensioner and the adjuster, not to a chain that has jumped. The control unit logs a code to match: a timing deviation, not a jumped chain.

It is not only the mileage that marks out the affected cars. The maker issued a service document for this in June 2013, and in it the examples with an engine number below 276 8xx 30 001281 or 276 9xx 30 406603 are the affected ones; that runs up to production in February 2013. The fault is also reported between 60 000 and 100 000 miles, that is between roughly 96 000 and 160 000 kilometres. Repairing the chain tensioner costs between 900 and 1300 pounds and the camshaft adjuster between 700 and 1100 pounds, and long cranking and misfires belong to the second job as well.

If it is left like this, the timing fault codes become permanent, the idle turns uneven, power drops and the repair grows larger. The diagnosis runs on live data: the workshop reads the real timing angle and looks at the freeze frame of the fault code.