P24DA: Particulate Matter Sensor Exhaust Sample Error Bank 1
What to do
Mention any recent exhaust work first — this code usually follows it. It says the sensor is not seeing a proper sample of the exhaust gas, and the commonest reason is a sensor not refitted quite right after a repair. That is a free fix if it is found before a new part is ordered.
Listen for a blowing or ticking noise from underneath, especially when cold. An exhaust leak ahead of the sensor lets air in and produces this fault with a perfectly good sensor — and it is worth reporting because it is easy to overlook on a ramp.
The car will drive normally. It is the emissions self-check that is affected, so allow time before an MOT.
What this code means
The particulate matter sensor is not receiving a representative sample of the exhaust gas.
This is a mechanical code wearing electrical clothing, and reading it correctly saves a wasted part. The sensor is working. Its heater works, its circuits are sound, its temperature channel is fine. What it is measuring is not the exhaust.
The sensor has to sit in the flowing gas stream to see what is in it. Its element protrudes into the pipe behind a protective shield, and anything that stops representative gas reaching that element produces this code.
- Incorrect installation — a sensor not seated to depth, or rotated so its shield openings face the wrong way, sits in still gas rather than moving gas.
- A blocked or crushed protective shield, which is easy to damage on refitting and blocks the sample without looking obviously wrong.
- An exhaust leak upstream, which lets the pipe draw air in and dilutes what reaches the sensor.
- Soot or condensate bridging the shield, which is a slow accumulation rather than a failure.
Almost every one of these is a consequence of recent work on the exhaust. Ask what was done and by whom before ordering anything, because a sensor refitted correctly resolves a large share of these at no parts cost.
Where nothing has been touched, look for the leak. A blowing joint or a corroded pipe upstream of the sensor is the usual finding on an untouched vehicle.
Likely causes
Start here
Less common
- Soot contamination in the sensor port · easy
- Faulty particulate matter sensor · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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