Mercedes OM651 diesel 220 CDI and 250 CDI (from 2009): early piezo injector failures
Press reports from 2009 to 2012, quoting Mercedes, describe failures of the piezo injectors of the new OM651 diesel in the 220 CDI and 250 CDI (C-Class, E-Class, GLK), with the engine warning light, uneven running and, at worst, limp-home mode. Mercedes attributed the cases to production-related electrical faults at its injector supplier and ran customer-service measures (injector replacement, warranty extension or vouchers depending on the country). It was not an official recall in France.
Dossier revision 1 · data updated 2026-10-13 · canon release 2026.10.1
At a glance
- Severity
- Major risk of being immobilised, or replacement of a major component.
Severity follows the worst documented outcome, not the average case. - Safety-relevant
- Not flagged as safety-relevant.
- In the Elgarde checklist
- Ordinary entry: it does not cap the verdict by itself.
- Documented in
- EU, UK
Which cars this covers
Only Mercedes OM651 diesels in the 220 CDI (170 hp) and 250 CDI (204 hp) versions of the C-Class (W204), E-Class (W212) and GLK, from the first cars built in 2009. Mercedes stated the 200 CDI, with magnetic injectors, is not affected. The French service measure covered cars built February to August 2009. The same engine in the SLK 250 CDI is treated as possibly affected; the sources do not name that model.
- Models in scope
- Mercedes-Benz C-Class, Mercedes-Benz E-Class, Mercedes-Benz GLK, Mercedes-Benz SLK
- Conditions on top of the model
- All of these must hold:
- Engine: Mercedes OM651 diesel, 220 CDI and 250 CDI versions
- Production date: from February 2009
- All of these must hold:
- Notes on scope
- Sources disagree on when piezo injectors were dropped: mbpassion (2025) says the 220 CDI changed to magnetic injectors from 2010 while the 250 CDI partly kept piezo elements to the end of the series, whereas AUTO BILD still reports injector failures in 2012. The end date is therefore left open. No recall record was found in RappelConso or in NHTSA for this injector issue (searched 13 October 2026). The customer-service measures were described in 2009 for Germany, France and the UK.
How to check whether a particular car is affected
Elgarde reads the conditions above and gives one of three answers for a car:
- Applies: every condition is confirmed for the car.
- Possible: at least one condition cannot be confirmed yet. The entry stays on the checklist, with a note on what to find out.
- Not applicable: a condition is clearly not met (for example a manual gearbox on a DSG entry). The entry is left off the checklist.
What to look for, and where
- Model: one of the models listed above
The model name as on the registration document, e.g. Golf, 208, 320d. - Engine code: Mercedes OM651 diesel, 220 CDI and 250 CDI versions
On the engine plate or block, or from a dealer VIN query. Displacement (P.1) and power in kW (P.2) on the registration certificate help narrow it down. - Production month: from February 2009
The month the car was built (on the VIN plate or in the registration papers). It only matters when the year alone does not settle it.
When in doubt, treat the car as possible: asking one question too many costs less than missing a defect.
How the fault arises, as reported
The OM651 220 CDI and 250 CDI used new-generation piezo injectors (2,000 bar). According to Mercedes, as quoted by AUTO BILD in 2009, technical analysis traced the cases mainly to production-related electrical faults of the injector, corrected at the supplier; AUTO BILD and L'argus name the supplier as Delphi, and L'argus says the manufacturer declined to answer its questions on this point. In January 2012 Daimler told AUTO BILD that the then-current failures came from contact problems at the connector, possibly after repeated injector replacement, and that the injector wiring harness was being replaced with an optimised part at inspections. Mercedes said the 200 CDI, with magnetically controlled injectors, was not affected.
Reported symptoms
Early signs
- Engine warning light and uneven running
- Jerking, unstable idle or cut-outs (L'argus)
Later signs
- Limp-home mode with reduced speed
What to check when inspecting a car
- Documents and records. Confirm the engine is the OM651 in a 220 CDI or 250 CDI and the build date (door-pillar label or dealer VIN query); the 200 CDI uses a different injector type.Red flag: 220/250 CDI built from 2009, especially February to August 2009.
- Documents and records. Ask for invoices of injector replacement (and of the injector wiring harness, which Daimler said was replaced free at inspections) and any goodwill paperwork.Red flag: No injector record on a 2009-2011 car.
- Diagnostic read-out. Read the fault memory, then run the engine warm and idle it, and test drive: look for the warning light, uneven running, jerking or limp-home mode.Red flag: Warning light, uneven running or limp mode: have the injectors checked by a Mercedes diesel specialist.
Repair and cost
- Usual remedy
- Injector replacement; Mercedes UK said in 2009 that it aimed to replace all the injectors of an affected car at once. In 2012 Daimler also described replacing the injector wiring harness with an optimised part at inspections.
- No published repair cost is recorded in this dossier.
What the manufacturer and regulators have said
Manufacturer programme
2009 customer-service measures reported by the press: France, a customer-satisfaction operation (not a recall) with injector replacement under warranty and a warranty extension of 1 year or 200,000 km as a commercial gesture; Germany, free replacement cars and a 200 EUR voucher; UK, a loan car for customers with more than one failure and a 250 GBP voucher or free first service. Terms for later years are not documented in the sources used here. Sources: [1], [2], [3], [4]
How common is it?
Manufacturer figure
- Figure
- 2,800
- Population
- Cases (Beanstandungen) of injector problems that Mercedes told AUTO BILD it had in Germany for OM651 220 CDI and 250 CDI cars with piezo injectors, October 2009
- Geography
- DE
- What was counted
- Cases reported to the manufacturer
- Confidence grade
- C: manufacturer, recall or large-survey figure; method only partly known
- Caveats
- Manufacturer figure for a count of cases, not a rate. L'argus reports the same 2,800 against 25,000 vehicles sold (without stating the area), while AUTO BILD says about 50,000 cars could theoretically be added; the denominators do not agree, so no percentage is given.
- Sources
- [1], [2]
No reliable figure
No reliable figure for how many cars are affected is recorded for this entry. This is stated on purpose: a missing number is not a low number.
No verified failure rate for OM651 piezo injectors has been published; the only figure is a manufacturer count of cases from 2009 with inconsistent denominators, and no later figure was found. Sources: [1], [2]
Evidence and sources
Each statement above traces to the sources below. Review status is shown for every source.
| Publisher | Title | Date | Type | Tier | Confidence | Links | Review |
|---|---|---|---|---|---|---|---|
| AUTO BILD | [1] Diesel-Probleme bei E-Klasse, C-Klasse und GLK: Ärger mit dem Mercedes-Wunderdiesel German magazine: piezo injectors of the OM651 in the 220 CDI and 250 CDI (C-Class W204, E-Class W212, GLK) fail, with the warning light and a limp-home programme; Mercedes told the magazine it had 2,800 cases in Germany and that about 50,000 cars could theoretically be added; Mercedes stated the 200 CDI uses magnetically controlled injectors and is not affected; Mercedes attributed the cases to production-related electrical faults of the injector, corrected at the supplier (named by the magazine as Delphi); free replacement cars were offered. | 2009-10-06 | Specialist press | 2 · press or analysis | medium | autobild.de opened 2026-10-13 Archive copy | automated source check 2026-10-13 |
| L'argus | [2] Mercedes Classe C, Classe E et GLK : ratés à l'allumage French magazine: Mercedes ran a service operation on the new OM651 220 CDI (170 hp) and 250 CDI (204 hp) because of a fault in the Delphi-developed piezo injection system (an assembly defect on a series of parts), described as electrical faults at the injector causing jerks, unstable idle or cut-outs. According to the manufacturer a little over 10% of models were concerned, 2,800 vehicles out of 25,000 sold; in France 700 vehicles built between February and August 2009 (C-Class, E-Class, GLK), while the first C 250 CDI Prime Edition cars of summer 2008 were not affected. In France it was a customer-satisfaction operation, not an official recall: injector replacement under warranty (2 h 30), plus a warranty extension of 1 year or 200,000 km as a commercial gesture; in Germany a 200 EUR voucher. The magazine says the manufacturer declined to answer its questions on the supplier point. | 2009-10-30 | Specialist press | 2 · press or analysis | medium | largus.fr opened 2026-10-13 Archive copy | automated source check 2026-10-13 |
| Cars UK | [3] Mercedes BlueEfficiency (OM651) - Injector Problems UK consumer motoring site quoting a Mercedes statement: a problem due to the manufacture of a small number of faulty diesel fuel injectors by its supplier can affect 220 CDI and 250 CDI C-Class and E-Class models with the new OM651 engine; it can show as the engine warning light, uneven running or, at worst, limp-home mode; a loan car and a 250 GBP voucher or free first service were offered to customers with more than one failure. The site (not Mercedes) names Delphi as the injector supplier. | 2010-01-25 | Specialist press | 2 · press or analysis | medium | carsuk.net opened 2026-10-13 Archive copy | automated source check 2026-10-13 |
| AUTO BILD | [4] Mercedes 220 CDI und 250 CDI: Wieder Ärger mit dem Wunderdiesel Follow-up article: after modifications the injector failures were reported again from autumn 2011, first by taxi operators. Daimler told the magazine that the current injector failures were caused by contact problems at the connector, possibly due to repeated injector replacement, and that the injector wiring harness is replaced free of charge for an optimised part during inspections. The article also reports water pump and timing chain issues on the OM651 and a widened goodwill period for the chain tensioner. | 2012-01-18 | Specialist press | 2 · press or analysis | medium | autobild.de opened 2026-10-13 Archive copy | automated source check 2026-10-13 |
| mbpassion.de | [5] Die Schwachstellen des Mercedes-Benz OM651 4-Zylinder Diesel German Mercedes enthusiast magazine: the early piezo injectors of the OM651 proved failure-prone (jerking, uneven running, higher consumption, worse emissions); according to the article the 220 CDI models were switched to magnetic injectors from 2010, while the 250 CDI partly kept piezo elements until the end of the series. This differs from other sources on the dates; treat the end of the piezo period as unclear. | 2025-12-01 | Specialist press | 2 · press or analysis | medium | mbpassion.de opened 2026-10-13 Archive copy | automated source check 2026-10-13 |
Automated source check: the source was opened and its claims, dates and figures were compared with this dossier by an automated check. It is not a human sign-off.
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Suggested citation
Elgarde, “Mercedes OM651 diesel 220 CDI and 250 CDI (from 2009): early piezo injector failures”, known-defect dossier om651.injectors, canon release 2026.10.1, CC-BY-4.0, https://elgarde.com/defects/om651.injectors/
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