The ECU has detected that the differential pressure sensor signal for the diesel particulate filter is out of its expected range or performing unreliably. This often means a failing sensor, but it can also point to wiring issues or a blocked DPF.
P246C means the DPF differential pressure sensor is reporting a voltage or pressure reading that falls outside the expected range. In most BMW diesels, this is a sensor or wiring fault — not a blocked filter. A replacement sensor typically costs £180–£380 fitted [PATTERN DATA], while a blocked DPF can cost £1,200–£2,200.
Do not let anyone sell you a new DPF until the sensor and wiring have been ruled out. Full diagnostic order below.
In a BMW common-rail diesel, the differential pressure sensor measures the pressure difference across the DPF. The ECU uses this to estimate soot load and trigger regenerations. P246C is set when the sensor signal is either too high, too low, or inconsistent — essentially, the ECU can't trust the reading. This could be because the sensor itself is faulty, the wiring is damaged, or the pressure hoses are blocked or leaking. Importantly, the code does not mean the DPF is blocked — it means the sensor signal is unreliable. That distinction is the difference between a £180 sensor and a £1,500 DPF, and it's why the diagnostic order below is critical. This code is common across N47, B47, N57 and B57 BMW diesel engines, and the diagnostic approach is similar regardless of engine. On N47 and B47 engines, the sensor is relatively accessible; on N57 it can be more buried, but replacement is still routine for a BMW specialist.
Ordered by how often each is the real culprit, with typical fitted costs. This is the order a BMW specialist will work through.
| Cause | Likelihood | Typical Cost (fitted) | Notes |
|---|---|---|---|
| Failed differential pressure sensor | Very High | £180–£380 | Most common; sensor fails electrically or becomes clogged with soot |
| Wiring or connector issue (corrosion, chafing) | Medium | £100–£250 | Often intermittent; inspection and repair may be cheaper than replacement |
| Blocked or leaking pressure hoses | Medium | £100–£300 | Hoses can become blocked with soot or crack, causing incorrect readings |
| Blocked DPF causing sensor to read out of range | Medium | £250–£450 (forced regen) or £1,200–£2,200 (new DPF) | The sensor may be fine; the filter is genuinely full |
| Software / calibration issue (rare) | Low | £80–£150 (reflash) | Sometimes a software update resolves the range/performance code |
Cost figures [PATTERN DATA] — indicative independent-specialist pricing, not drawn from our engine replacement dataset.
Inspect for corrosion, damage, or loose pins. Many P246C codes are caused by simple wiring faults that cost almost nothing to fix.
Check the hoses connecting the sensor to the DPF for blockages or cracks. Often they get clogged with soot, causing false readings.
A specialist will compare the pressure reading at idle and under load against expected values. If it's consistently implausible, the sensor is likely faulty.
If the sensor is identical to another (e.g., on a twin-sensor setup), swapping them can confirm a sensor fault — if the code moves, replace the sensor.
Use diagnostic software to read actual DPF pressure and calculated soot mass. If the pressure is high and soot load is excessive, a forced regen may be needed.
Our diagnostic wizard walks the same order, or check your engine with the registration lookup.
Yes — in most cases, it's safe to drive short distances. P246C on its own is not an engine-destroying code. The ECU may limit performance to protect the DPF, but you won't cause immediate damage. However, if the code is accompanied by a flashing glow-plug light or the car enters limp mode, you should avoid motorway driving and get it looked at within a few days. Prolonged driving with a faulty sensor can lead to incorrect regeneration cycles, which may eventually clog the DPF — turning a cheap sensor repair into an expensive filter replacement. On B47 and B57 engines, the sensor is relatively easy to replace; on N57 it's a little more labour-intensive, but still a manageable job for a specialist. Get it diagnosed promptly — the cost gap between a sensor and a DPF is large.
Yes, for short journeys — but not for extended motorway use if the car has gone into limp mode. Prolonged driving with a faulty sensor can lead to incorrect DPF regenerations and eventual blockages.
No. In most cases, the sensor or wiring is at fault. Replacement of the sensor (around £180–£380) is far cheaper and resolves the code in the majority of cases.
It ranges from £100–£250 for wiring/hose repairs, £180–£380 for a sensor replacement, and up to £1,200–£2,200 for a full DPF replacement if the filter is genuinely blocked.
Only temporarily. The code will return if the underlying fault (sensor, wiring, hoses, or DPF) is not addressed. Clearing it also erases freeze-frame data that a specialist would use to pinpoint the cause.
Cheapest-First AlwaysWe rank causes by likelihood and cost, not by what's profitable to quote.
Honest About CostWe don't scare you into a new DPF; a sensor is often the only fix.
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