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OM654 engine: faults and reliability

Mercedes-Benz OM654 (2.0 diésel) · Mercedes-Benz

The OM654 is the 2.0-litre four-cylinder diesel with which Mercedes-Benz replaced the OM651 from 2016, fitted to most of its passenger cars and mid-size vans. It has a reputation for reliability: we found no mechanical faults as serious and widespread as on the brand's earlier diesels, although there were recalls for the timing chain (units from 2016 to 2021) and the coolant pump, and the NOx sensor or AdBlue system fail with some frequency.[1][2][3][4]

Risk index
63
High risk · what it is
Documented faults
4
3 of high or critical severity
Timing
Chain
Technical data[1][2]
Production
since 2016
9 models on this site

12 sourcesHow we work

Which OM654 versions should you buy?

Our verdict for each version, based on the documented faults.

  • OM654 first generation (2016-2021)

    2016–2021 · 120–194 hp

    With caution

    It is the generation covered by the timing chain recall, and it shares with the rest of the engine the less well documented risk of the vacuum-operated coolant pump and NOx/AdBlue sensor failure. You should check with an official dealer whether the vehicle falls within the campaign's production range and whether it has already been repaired.[3][4]

  • OM654 M, with 48 V mild hybrid (since 2021)

    since 2021 · 163–272 hp

    With caution

    The first generation's timing chain problem is not documented on these units, but NOx sensor or AdBlue system failure is still cited as the fault owners report most often in the reliability samples consulted, and we have not been able to confirm whether the warning about the vacuum-operated coolant pump also affects this generation.[3][4][5]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

Known faults of the OM654

Sorted from most to least important (severity × frequency).

  1. 1Critical severityFrequency: CommonTimingTiming chain wear or breakage (2016 to 2021 units)Yes: Mercedes-Benz recalled OM654 units built between January 2016 and February 2021 because the timing chain can wear and even break, risking engine damage. The campaign has already been carried out at official workshops; you should check whether the vehicle received it.
  2. 2Critical severityFrequency: OccasionalCoolingLeak in the vacuum-operated coolant pump (overheating risk)Mercedes-Benz recalled vehicles with the OM654 and OM656 engines because the vacuum-operated coolant pump can lose its seal between the coolant circuit and the vacuum circuit, with a risk of overheating and, in the worst case, fire.
  3. 3High severityFrequency: OccasionalTurboWear of the turbocharger and charge-air intercoolerThe OM654's variable-geometry turbocharger and its intercooler can start to fail from around 75,000 km, with loss of power or whistling noises. It is not the engine's most cited fault, but it appears recurrently across several models that use it.Appears at around 74,000 km
  4. 4Medium severityFrequency: CommonEmissions controlNOx sensor failure and SCR/AdBlue system warningsIt is the fault OM654 owners cite most across several models: the NOx sensor or the AdBlue injector/doser in the exhaust aftertreatment system (SCR) fails, and an emissions-related warning light comes on. It does not usually immobilise the car straight away, but it should be checked soon.Repair (garage): €700–€850Appears at around 85,000 km

Severity colours: low, medium, high, critical. How we rate them

By part

Compare each fault with the same part on other engines: symptoms, cost and affected models.

Symptoms of these faults

What the OM654 is

The OM654 is an inline four-cylinder diesel engine that Mercedes-Benz introduced in 2016 as the replacement for the OM651. It has an aluminium block and cylinder head, a low-friction coating (Nanoslide) on the cylinder walls, chain-driven twin overhead camshafts, a stepped combustion chamber, common-rail injection of up to 2,050 bar in the original version (2,700 bar in the 2021 update) and a water-cooled variable-geometry turbocharger. According to the brand itself, it is about 35 kg lighter than the OM651 it replaces.[1][2]

Mercedes-Benz first introduced it in the E-Class (W213) in April 2016 and extended it with subsequent updates: the CLS (C257) received it at its April 2018 launch, the C-Class (W205) in the July 2018 facelift, the GLC (X253) in the April 2019 facelift and the Vito (W447) from May 2019. The Sprinter van, in the generation launched in 2018 (907/910), did not use it until autumn 2021, when it became standard across all diesel variants.[2][6][7]

From 2021, Mercedes-Benz began introducing an updated version of the engine (informally identified as the "OM654 M"), with an integrated 48-volt starter-generator (EQ Boost mild-hybrid system), injection pressure raised to 2,700 bar and a slight increase in displacement, from 1,950 to 1,993 cc. This version has been fitted to the C-Class (W206) since June 2021 and the second-generation GLC (X254) since 2022, among other models.[2][8]

It has a reputation for being more reliable than Mercedes-Benz's earlier diesels: with the sources consulted, we have not found serious, widespread mechanical faults as clear-cut as those of the OM642 or the OM651. Even so, a German website specialising in used cars documents that the manufacturer recalled units built between January 2016 and February 2021 over a risk of timing chain breakage, and, separately, vehicles with this engine (and the six-cylinder OM656) over a possible leak in the vacuum-operated coolant pump. In day-to-day use, the fault owners cite most in several reliability samples is failure of the NOx sensor or the AdBlue system.[3][4][5][9][10]

Manufacturer
Mercedes-Benz (Daimler)
Family
OM654
Fuel
Diesel
Displacement
1,950 cm³
Cylinders
4
Fuel system
Turbo
Injection
Common rail
Timing
Chain
Power
116–272 hp
Peak torque
550 Nm
Production
since 2016
Makes
Mercedes-Benz

Technical data[1][2]

What changed between versions

  1. 2016–2021

    OM654 first generation (2016-2021)

    First generation of the engine, without a mild-hybrid system, with a displacement of 1,950 cc (there was also a 1.6 variant and a transverse "OM654q" for other group platforms, not present in the cars in this report). A specialist German website documents that Mercedes-Benz recalled units from this production period (January 2016 to February 2021) over a risk of timing chain breakage.[2][3]

  2. since 2021

    OM654 M, with 48 V mild hybrid (since 2021)

    Version with an integrated 48 V starter-generator (EQ Boost), injection pressure raised to 2,700 bar and displacement increased to 1,993 cc. In the sources consulted, we have not found the timing chain problem documented on the first generation continuing to appear on these units, which suggests (although we cannot confirm it explicitly) a design change.[2]

Cars fitted with the OM654

9 models sold in Europe. Open each one to see all their faults and the buying checklist.

Mercedes-Benz

Compare the OM654

Maintenance parts for the OM654

The parts replaced at services and when the timing belt or chain is changed, searched for this engine. Confirm the part number with the registration plate or VIN.

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Sources

Every fact on this page links to its source. If you find an error, let us know.

  1. Mercedes-Benz OM654 engineWikipedia · Other source · consulted 27 September 2026
  2. Mercedes-Benz OM 654Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
  3. Mercedes-Benz GLC (X253): Alle typischen Probleme & MängelGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
  4. Fiabilité Mercedes Classe E (2016-2023)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  5. Fiabilité Mercedes GLC (2015-2022)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  6. Mercedes-Benz SprinterWikipedia · Other source · consulted 27 September 2026
  7. Mercedes Sprinter (2022): Neuer OM654-Diesel für alle Variantenfirmenauto.de · Motoring press · published July 2021 · consulted 27 September 2026 · in German
  8. Mercedes-Benz GLCWikipedia · Other source · consulted 27 September 2026
  9. Fiabilité Mercedes Classe C (2014-2021)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  10. Fiabilité Mercedes GLC Coupé (2016-2023)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
  11. Mercedes-Benz C-Class (W205)Wikipedia · Other source · consulted 29 October 2026
  12. Mercedes-Benz V-KlasseWikipedia (alemán) · Other source · consulted 27 September 2026 · in German