P244B is a common DPF temperature sensor fault code on Mercedes diesel models. It means the ECU has detected that the temperature sensor signal voltage is too high – but that can be caused by a faulty sensor, a short circuit, or a wiring issue. This page breaks down the causes ranked by cost, what to check first, and whether you should keep driving.
P244B means the ECU is seeing a high voltage signal from the DPF temperature sensor – typically because the sensor has failed internally (short circuit), the wiring is shorted to battery voltage, or the sensor is reading an implausibly high temperature. On most Mercedes diesels, this is a sensor or wiring issue long before it indicates a DPF problem.
Do not assume the DPF itself is faulty – a simple £150 sensor replacement or a wiring repair often fixes it. Full diagnostic order below.
In a Mercedes diesel equipped with a DPF (Diesel Particulate Filter), the ECU monitors exhaust gas temperature using one or more temperature sensors located before and after the DPF. P244B is logged when the voltage signal from the sensor is higher than expected – this typically indicates an internal short circuit in the sensor, a wiring short to battery voltage, or a sensor reading a temperature that is implausibly high. The code is a diagnostic flag, not a death sentence – it tells you the system has a high voltage signal problem, but it doesn't tell you whether the sensor is faulty, the wiring is damaged, or the ECU is reading incorrectly. This code appears across the full range of Mercedes common-rail diesels, from the OM651 four‑cylinder to the OM642 V6 and the newer OM654, and the diagnostic approach is similar regardless of which engine triggers it.
Ordered by how often they are the real culprit – and by typical cost, so you can sanity-check any quote you've been given.
| Cause | Likelihood | Typical Cost (fitted) | Notes |
|---|---|---|---|
| Failed DPF temperature sensor (internal short) | Very High | £100–£250 | Common failure; replacement is straightforward and inexpensive |
| Wiring short to battery voltage | Medium | £150–£400 | Chafing or damaged insulation can short the signal wire to power |
| Poor electrical connection / corroded plug | Medium | £50–£150 | Corrosion can create a high-resistance connection that causes voltage issues |
| ECU internal fault (rare) | Low | £500–£800 | Very rare; the ECU itself may be reading incorrectly |
| Genuine DPF overheating | Low | £900–£1,500 | If the DPF is genuinely overheating, the sensor reading may be correct – inspect for blockages |
Cost figures [PATTERN DATA] – indicative independent‑specialist pricing, based on common Mercedes DPF sensor repairs.
Inspect the connector for corrosion, bent pins, or loose connections. Check for visible wiring damage – chafing against engine parts can cause shorts.
A specialist can read the sensor voltage and compare it to expected values. A reading consistently close to 5V (or battery voltage) suggests a short.
Using a multimeter, test the sensor resistance against manufacturer specifications – an internal short will show abnormally low resistance.
With the sensor disconnected, test for continuity between the signal wire and battery voltage – if present, the wiring has a short.
If the sensor and wiring are fine, the ECU may be at fault, or the DPF may be genuinely overheating.
Our diagnostic wizard follows the same order, or confirm your engine with the registration lookup.
Conditionally, yes – but get it diagnosed within days. P244B on its own is not an engine-destroying fault, but if the ECU cannot read the temperature correctly, DPF regeneration may fail. Over time, this can lead to a blocked DPF and expensive repairs. Short journeys to a specialist are acceptable, but if the DPF warning light is also flashing or if the vehicle is in limp mode, prolonged driving is not recommended.
Short journeys to a garage are generally fine, but if the vehicle displays a DPF warning or has entered limp mode, you should get it checked promptly. Prolonged driving with an inaccurate temperature reading can prevent DPF regeneration and cause the filter to block.
No – wiring shorts to battery voltage are also common. A simple wiring repair or a £150 sensor replacement often fixes it.
Only if the underlying problem is temporary (e.g., a one-off voltage spike). The code will return if the fault persists, and clearing it may destroy freeze‑frame data that helps diagnosis.
Expect £100–£250 at an independent Mercedes specialist – parts are inexpensive and labour is typically under 1 hour.
For Mercedes, the repair‑to‑value threshold is 70% – if the cost of the repair (including diagnostics and parts) exceeds 70% of the car's current market value, scrapping may be the more sensible financial decision. Always get a current valuation before committing to major work.
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