2.2 CDI (OM646) vs 2.2 HDi: which engine is more reliable?

According to our risk index, the 2.2 CDI (OM646) carries less risk than the 2.2 HDi: 46/100 versus 48/100 (both moderate risk). The 2.2 CDI (OM646) has 1 documented serious fault, the main one being «Injector seal leak with carbonisation around the seat»; the 2.2 HDi has 3 documented serious faults, the main one being «DPF clogging with additive, especially on the 128-138 hp version».

Risk index

2.2 CDI (OM646)

Moderate risk · 1 serious fault

Lower risk

Risk index

2.2 HDi

Moderate risk · 3 serious faults

The index (0–100) weights the severity and frequency of the three most serious documented faults. How it is calculated

Reviewed on 27 September 202616 sources How we work

Is the 2.2 CDI (OM646) reliable?

The OM646 is the 2.2 CDI four-cylinder diesel that Mercedes-Benz fitted between 2002 and 2010 to the C-Class, E-Class, Vito/Viano and Sprinter, as the successor to the OM611 (1998-2006). It is a fundamentally sound engine, considered robust in its mechanical base, but with known and well-documented faults: leaks at the injector seals, a clogged EGR valve, particulate filter sensor failures and a short-lived water pump on some versions.^[1][2][3][4]

See the 6 of the 2.2 CDI (OM646) faults

Is the 2.2 HDi reliable?

This is a diesel derived from the 2.0 HDi that PSA and Ford shared in large saloons and MPVs (407, 607, 807, C5, C6, C8) and that Land Rover and Ford used under their own names (TDCi, TD4, SD4) in the Mondeo IV, the Freelander 2 and the first Evoque. According to fiches-auto it does not suffer chronically from the turbo or dual-mass flywheel problems of smaller HDi engines, but the 128-138 hp version does have a recurring problem of DPF clogging.^[5][6][7][8]

See the 4 of the 2.2 HDi faults

Side-by-side comparison

Comparison of 2.2 CDI (OM646) and 2.2 HDi
Item	2.2 CDI (OM646)	2.2 HDi
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	2,148 cm³	2,179 cm³
Timing	Chain	Timing belt (dry)
Power	82–170 hp	128–204 hp
Production	1998–2010^[1][9][10]	2000–2015^{[5][7][11][12][13]}
Reliability
Risk index (what is it?)	46Moderate risk	48Moderate risk
Documented faults	6	4
Of high or critical severity	1	3
Worst severity	High severity	High severity
Main faults	High severity: Injector seal leak with carbonisation around the seat Medium severity: EGR valve clogged or seized by soot Medium severity: Leak and premature failure of the water pump	High severity: DPF clogging with additive, especially on the 128-138 hp version High severity: Turbo faults, somewhat more frequent on the sequential twin-turbo versions High severity: Piezo injector wear and failure
Most expensive documented repair	up to €300Faulty air flow meter on the 220 CDI (OM 611 and OM 646)Published figure^[14]	No reliable data
Which versions to buy
BuyRecommended versions	None	2.2 HDi 150-156 (single variable-geometry turbo, 2006-2012)^[15][16]
With cautionVersions to be cautious about	OM611 (predecessor, 2.2 CDI, 1998-2006)^[2][4] OM646 pre-EVO (2002-2007, Euro 3/4, 88-150 hp)^[2][3][4] OM646 EVO (2006-2009, up to 170 hp)^[4]	2.2 HDi 128-138 (DW12 TED4, single turbo, 2000-2006)^[8] 2.2 HDi 170-175 twin-turbo (DW12 BTED4, 2005-2010)^[8][12] 2.2 HDi 190-204 twin-turbo (DW12 C, 2010-2015)^[12]
AvoidVersions to avoid	None	None

Severity of each fault: green, low; amber, medium; red, high; dark red, critical. How we rate them

Cars that each one is fitted to

2.2 CDI (OM646)

2.2 HDi

See the 12 models with the 2.2 HDi

Other comparisons

With the 2.2 CDI (OM646)

With the 2.2 HDi

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Sources

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

Mercedes-Benz OM 646/OM 647/OM 648Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Mercedes C-Klasse W203 – Typische Probleme & SchwachstellenGebrauchtwagenberater · Motoring press · consulted 27 September 2026 · in German
Fiabilité 200 CDI MercedesFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité 220 CDIFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
PSA EW/DW engineWikipedia (inglés) · Other source · consulted 27 September 2026
Ford MondeoWikipedia (francés) · Other source · consulted 27 September 2026 · in French
Land Rover FreelanderWikipedia (francés) · Other source · consulted 27 September 2026 · in French
Essai, avis et fiabilité des 2,2 HDI 136 chevauxFiches-Auto · Motoring press · consulted 27 September 2026 · in French
Mercedes-Benz OM646 engineWikipedia · Other source · consulted 27 September 2026
Mercedes-Benz OM611 engineWikipedia · Other source · consulted 27 September 2026
Range Rover EvoqueWikipedia (inglés) · Other source · consulted 27 September 2026
Essai, avis et fiabilité des 2,2 HDI 204 chevauxFiches-Auto · Motoring press · consulted 27 September 2026 · in French
Essai Citroën C5 Exclusive + 2.2 HDI 200 TourerActu Automobile · Motoring press · published 2011 · consulted 27 September 2026 · in French
Caudalímetro o sensor MAF: qué es, cómo funciona y cuáles son las averías más frecuentesDiariomotor · Motoring press · consulted 30 October 2026 · in Spanish
Essai Peugeot 4007 2.2 HDi DCS 6Caradisiac · Motoring press · published 7 April 2010 · consulted 27 September 2026 · in French
Citroën C-CrosserWikipedia (español) · Other source · consulted 27 September 2026 · in Spanish