Exhaust, catalytic converter and particulate filter
An exhaust system is more than a pipe: the catalytic converter, the oxygen sensors and, on a diesel, the particulate filter are part of engine management, and a fault there shows up immediately in consumption and power. The particulate filter burns itself clean in use, but only if it gets hot enough — on nothing but short trips that never happens, and over time it clogs.
What it covers
- Checking the system for leaks, particularly at the flanges and manifold
- Measuring the oxygen sensors in operation rather than only reading the fault code
- Reading the particulate filter's soot load and forcing a regeneration where needed
- Replacing mounts and rubber hangers before the system starts knocking
What tells you it is due
- The note gets louder or drones at certain revs
- The particulate filter light comes on and consumption rises
- The engine pulls less willingly at higher revs
- A rattle under the car when pulling away — usually a broken mount or a loose heat shield
Worth knowing
When the particulate filter light appears, the right response is not a workshop appointment in two weeks but a longer drive at higher revs so the regeneration can complete. If the light stays on afterwards, the car belongs in a workshop. Carry on doing short trips and unburnt fuel ends up in the engine oil — and that is the more expensive damage.
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