P2452 and P2453: DPF differential pressure sensor circuit

The ECU has no direct way to see inside a particulate filter. It infers soot loading from the pressure difference across the filter: a clean filter passes gas freely, a loaded one restricts it, and the pressure drop rises.

That entire strategy depends on one differential pressure sensor.

Code	Meaning
P2452	DPF pressure sensor circuit
P2453	Range/performance
P2454	Circuit low
P2455	Circuit high

Related: DPF diesel particulate filter diagnostics.

The two failure directions

Reading too high. The ECU believes the filter is loaded when it is not, and triggers regeneration repeatedly. Consequences: wasted fuel, thermal stress on the filter, and oil dilution from post-injection.

Reading too low. The ECU believes the filter is clean when it is loading, and never regenerates. Consequences: the filter fills until it genuinely blocks, and by the time a warning appears the situation is expensive.

Both are worse than they sound, and neither is obvious to the driver until it is advanced.

The blocked-pipe problem

This deserves its own section because it is the most common physical cause and the cheapest fix.

The sensor does not sit in the exhaust. It connects to it through two small metal pipes, one before and one after the filter, with short rubber sections at the sensor end.

Those pipes:

• Block with soot, particularly on vehicles doing short journeys.
• Corrode and split, letting pressure escape.
• Crack at the rubber joints, which harden with heat.

A blocked pipe means the sensor reads a pressure difference that does not exist. The sensor is fine, the reading is wrong, and replacing the sensor changes nothing.

Check and clear the pipes before ordering anything. This one check resolves a meaningful share of these codes.

The key-off test

Simple and decisive.

With the engine off, differential pressure across the filter must be zero. No exhaust flow means no pressure drop.

Key-off reading	Verdict
Zero, or very close	Sensor plausible
A significant value	Sensor faulty or pipe blocked
Negative	Circuit fault, or pipes swapped
Same as when running	Stuck sensor

That last case appears after work where the two pipes were reconnected the wrong way round — worth checking on any vehicle that has recently had exhaust work.

What plausible readings look like

Approximate, and specific to engine size and filter design:

Condition	Expected differential
Engine off	0
Warm idle, clean filter	A few millibar
Warm idle, loaded filter	Noticeably higher
High RPM, clean filter	Rises with flow
High RPM, loaded filter	Rises steeply

The relationship with flow is what matters. A pressure that does not change between idle and high RPM is a blocked pipe or a dead sensor, whatever the absolute number.

Symptoms

• DPF warning lamp with no obvious cause.
• Regeneration attempts far more often than normal — every 100 km rather than every 500.
• No regeneration at all, with soot load climbing steadily.
• Reduced power.
• Rising oil level from repeated post-injection: oil light flickering at idle.

Check the oil level on any diesel with repeated regeneration attempts. Above maximum means change it — diluted oil does not protect bearings.

Reading it alongside the rest

Codes	Interpretation
P2452 alone	Sensor or pipes
P2002 alone	Genuine filter efficiency problem
P2452 + P2002	Fix the sensor first, then re-assess
P242F	Ash, not soot — a different conversation
EGT sensor codes	Regeneration cannot be verified: P2031 to P2036

In what order

1. Read differential pressure with the engine off — it must be zero.
2. Inspect and clear both sensor pipes.
3. Check the rubber joints at the sensor.
4. Confirm pressure rises with RPM on a warm engine.
5. Check the connector for corrosion.
6. Compare soot load with what the pressure implies.
7. Replace the sensor only after the pipes are proven clear.

Read DPF differential pressure with the ignition on and the engine off — an ELM327 adapter and the free tier of the app are all it takes. A non-zero number there means you have found the fault without removing a single component.