The wiring harness running under the driver's seat kinks and breaks from the seat being adjusted. The sign is the airbag light staying on on the dash. With the airbag light on the system will not work in a crash, and it fails the roadworthiness test too. The part is cheap, the fault finding is the expensive bit, and many sellers mention it as "just a light".

The light, magnesium cased MQ200 and the MQ250, sized for higher torque, are the most widespread manual gearboxes in the transverse engine VAG models. Both have the same two weak points, and both depend on use.

The door seal ages, and the water runs into the front footwell. It stays in the foam under the carpet, so for a long time only the misting windows and the musty smell show it. The comfort control unit and several connectors run in the footwell: if they corrode, the fault is electrical from then on.

The rear calipers seize: the pad does not release, the disc overheats and turns blue, the car pulls to one side under braking, and the fuel consumption rises unnoticed. On salted winter roads it develops faster. The symptom is easy to mistake for simple pad wear, but a seized caliper takes the disc with it, and often the wheel bearing too.

The G62 sensor tells the engine control unit how hot the coolant is. If it is faulty, the control unit thinks a warm engine is cold, and runs it rich: hard warm or cold starting, a rough idle, markedly increased fuel consumption, and a dash temperature gauge that jumps around or never reaches its usual reading. The part is cheap and can be replaced in half an hour: the trouble is that many people do not recognise it and replace an injector or a lambda sensor instead. If the fault persists, the rich mixture can destroy the catalytic converter too.

From the late nineties to around 2006, petrol engines used a secondary air pump to blow fresh air into the exhaust on a cold start, so the catalytic converter reaches operating temperature faster. The impeller of the pump rusts or its bearing seizes, soot clogs the combination valve (N112), and the rubber hoses crack. The control unit then stores the `P0411` code. It barely affects driving, but the engine warning light is on, and the emissions test can fail because of it, and the roadworthiness test with it.