P244A: Particulate Filter Differential Pressure Too Low Bank 1
What to do
The car will very likely feel completely normal, and that is the point of getting it looked at. This code says the filter may not be filtering — which is an MOT and emissions problem rather than something you will notice from the driver's seat.
The usual cause is a pair of small pressure hoses, which is a cheap repair, so do not assume the worst before it has been inspected.
If this vehicle has been bought recently, mention that. A hollowed-out filter is a known way of disguising a failed one before a sale, and it produces exactly this reading. A garage can tell the difference by looking; you cannot.
What this code means
The pressure difference across the particulate filter is lower than a working filter should ever produce.
A filter is a restriction, and that is the point of it. Gas entering it is at a measurably higher pressure than gas leaving it, and the module watches that difference to judge how full the filter is. A difference of almost nothing means the gas is not being filtered.
There are three explanations and they are very different in cost.
- The sensor or its pipework is at fault — the two small hoses that carry pressure from the exhaust to the sensor block with soot, split, or get swapped. This is the commonest cause and the cheapest.
- There is a leak between the two measuring points, so both hoses see much the same pressure regardless of the filter.
- The filter substrate has failed or been removed. A cracked or melted core, or a shell that has been hollowed out, passes gas freely — and reads exactly like this.
That last case is why this code matters more than its symptoms suggest. The car will usually drive perfectly, and a filter that is not filtering is emitting everything it was fitted to catch.
Check the hoses before anything else, including that they are on the right ports: reversed hoses produce a reading that is wrong in a way no amount of sensor replacement fixes.
Likely causes
Start here
Less common
- Pressure sensor hoses fitted the wrong way round · easy
- Cracked or failed particulate filter substrate · specialist
- Exhaust leak upstream of the sensor · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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