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Mercedes-Benz OM654.920/921 Engine - Replacement Cost, Problems & CompatibilityProblems & Compatibility
The OM654 is Mercedes-Benz’s modern 2.0-litre inline-4 common-rail diesel (CDI), fitted to the W205 C-Class, W213 E-Class, and X253 GLC. Reconditioned OM654 engines typically start from £3,000 , and with 520 UK replacement requests in 2025 , it remains a highly sought-after unit for premium Mercedes repairs and high-mileage fleet rebuilds.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
Used from
£1,800
Reconditioned from
£3,000
Rebuilt from
£4,200
GB
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Key Specs
Mercedes-Benz OM654.920/921 - Specifications at a Glance
Engine Code
OM654.920 / OM654.921
Fuel
Diesel
Configuration
2.0L inline-4, DOHC, 16-valve, common-rail (CDI)
Power Output(s)
110 kW (150 hp) - 143 kW (194 hp)
Years Produced
2016-Present
UK Models Fitted
3 Mercedes model families - full list in Compatibility below
2025 UK Replacement Requests
520
Replaced
OM651
Replaced By
Still in production (OM656 for 6-cylinder roles)
Most Common Failure
AdBlue system faults and EGR cooler leaks
Reconditioned Price Range
£3,000-£5,000 supply-only
Vetted UK specialists for OM654.920/921 replacements
Minimum 12-month warranty on reconditioned and rebuilt options
Fitted To
Which Mercedes Models Use the OM654.920/921-
The OM654 is the definitive modern 4-cylinder diesel for Mercedes-Benz, offering improved emissions compliance, better fuel economy, and a more modular design compared to the older OM651 it replaced.
| Model | Generation/Chassis | Badge(s) | Years | Link |
|---|---|---|---|---|
 Mercedes-Benz C-Class | W205 | C 200 d, C 220 d | 2016-2021 | |
| Mercedes-Benz E-Class | W213 | E 200 d, E 220 d | 2016-2023 | |
| Mercedes-Benz GLC-Class | X253 | GLC 200 d, GLC 220 d | 2016-2022 |
02
Mercedes-Benz E-Class
03
Mercedes-Benz GLC-Class
CROSS-BRAND
OM654.920/921 is documented across 3 BMW applications spanning C-Class, E-Class, GLC-Class. Registration lookup confirms the exact suffix before quotes are sent.
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Prices
Mercedes-Benz OM654.920/921 Engine Replacement Cost (UK)
Condition | Supply Only | Fitted (Independent Specialist) | Typical Warranty |
|---|---|---|---|
Used | £1,800-£3,200 | £2,320-£3,980 | 3-6 months |
Reconditioned | £3,000-£5,000 | £3,520-£5,780 | 12-24 months |
Rebuilt | £4,200-£6,500 | £4,720-£7,280 | 12-24 months |
What genuinely moves the price for this engine is the condition of the AdBlue system, EGR cooler, and turbocharger. Because the OM654 is a highly complex modern common-rail unit, recon specialists will typically verify the AdBlue dosing module, replace the EGR cooler if necessary, and update all software maps as standard. For a full breakdown of market rates, see our full reconditioned engine cost guide.
Labour Guide
Fitting an OM654 engine typically takes 8-12 hours at £65-£85/hr (independent) - confirm exact labour when comparing quotes.
Price Factors
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Common Problems
Mercedes-Benz OM654.920/921 Engine Problems - What Actually Fails
Every engine has its weak points. Here are the known issues with the OM654.920/921, based on real-world data and verified failure patterns.
Verified issue focus: AdBlue system faults and EGR cooler leaks.
1. AdBlue System Faults
1. AdBlue System Faults
Typical onset:
80,000-150,000 miles
What happens:
The AdBlue dosing module or NOx sensors can fail, leading to warning lights, restricted performance (limp mode), and eventually a no-start condition if the tank is depleted and the system is locked out by the ECU.
Repair vs replace:
Often resolved by replacing the dosing module or NOx sensor, which is a standard repair. If the tank heater or pump has failed, a full tank assembly replacement may be required.
Read more about this issue
2. EGR Cooler Leaks
2. EGR Cooler Leaks
Typical onset:
80,000-150,000 miles
What happens:
The internal matrix of the EGR cooler can crack, allowing coolant to mix with exhaust gases or enter the intake manifold. This leads to unexplained coolant loss, white smoke from the exhaust, and potential hydrolock if severe.
Repair vs replace:
EGR cooler replacement is a standard repair. If caught early, it prevents catastrophic internal engine damage.
Read more about this issue
3. Occasional Timing Chain Wear
3. Occasional Timing Chain Wear
Typical onset:
100,000+ miles
What happens:
While significantly improved over the OM651, some high-mileage OM654 units can exhibit timing chain stretch or guide wear, leading to a faint rattle on cold starts.
Repair vs replace:
If caught early, a timing chain kit replacement is straightforward. If ignored, it can lead to valve-to-piston contact, requiring a full engine replacement.
Read more about this issue
The OM654 is generally considered a highly robust and reliable modern diesel. Units maintained with strict AdBlue top-ups and regular oil changes routinely exceed 150,000 miles without major internal issues .
Compare rebuilt OM654.920/921 engine prices with the failure already addressed
Engine Variants
How to Confirm You Have the Mercedes-Benz OM654.920/921
The engine code is stamped on the right-hand side of the cylinder block, near the oil filter housing. It will also be listed on your V5C logbook under "Engine Capacity" or visible via a VIN decode. The OM654.920 and .921 are the primary 2.0L variants of the OM654 family. They are sometimes confused with the older OM651 or the larger OM656 inline-6. Fitting the wrong revision or assuming interchangeability matters significantly: the OM654 features a specific modular design, distinct AdBlue/SCR plumbing, and ECU mapping that will not function correctly if swapped with an OM651 or OM656 without extensive and costly modification.
Not sure which engine your car has- Enter your registration above - we'll confirm your exact OM654.920/921 fitment before any quotes are sent.
Easily Confused
OM651
the 2.1L inline-4 CDI that the OM654 replaced, offering improved modular design and emissions compliance but sharing some similar thermal management challenges.
Alternative / Next-Gen Code
OM654.930/940
the updated variant of the same OM654 family, featuring revised mild-hybrid integration and updated emissions hardware for the latest chassis applications.
Related JLR Variants
OM656
the modern 3.0L inline-6 CDI that took over the flagship 6-cylinder diesel role, sitting above the OM654 in the hierarchy for heavier chassis applications.
Confirm the exact OM654.920/921 fitment
Not sure which engine your car has- Enter your registration above - we'll confirm your exact OM654.920/921 fitment before any quotes are sent.
Buying Guide
Buying a Replacement OM654.920/921 Engine - What to Choose
Choosing the right replacement route depends on your budget, risk tolerance, and ownership goals. Here's a breakdown of your options.
Used:
A used OM654.920/921 engine makes sense only if it comes with verifiable service history and documented proof that the AdBlue system and EGR cooler are in good working order. Given the complexity of modern emissions systems, buying a used unit with unknown history is a significant financial risk.
Reconditioned:
A proper reconditioned OM654 engine is the sweet spot for most buyers. A reputable rebuild will proactively address the common failure points by verifying the AdBlue dosing module, replacing the EGR cooler, and refreshing all critical seals, giving the engine a fresh lease on life.
Rebuilt:
A full OM654 engine rebuild is justified for high-mileage W213 E-Class or X253 GLC hosts where maximum longevity and originality are required. An upgraded rebuild should include line-boring the block, new pistons/rings, and a balanced crankshaft.
Supply & Fit Line:
Sourcing and fitting through our vetted network ensures your OM654 engine is installed by specialists familiar with modern Mercedes CDI systems, backed by a nationwide warranty.
Vehicle Value Note:
Because the OM654 is typically found in W205, W213, and X253 vehicles valued between £8,000 and £30,000, a full replacement is generally financially viable and comfortably within the host vehicle's value . Replacement cost rarely exceeds the scrap threshold for these modern chassis, making a reconditioned unit a highly sensible investment.
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Related Engines
Engines Related to the Mercedes-Benz OM654
Explore engines that are closely related to the Mercedes-Benz OM654.920/921, including its predecessor, successor, and key family variants.
Predecessor
OM651
the 2.1L inline-4 CDI that the OM654 replaced, offering improved modular design and emissions compliance but sharing some similar thermal management challenges.
Successor
OM654.930/940
the updated variant of the same OM654 family, featuring revised mild-hybrid integration and updated emissions hardware for the latest chassis applications.
Sibling
OM656
the modern 3.0L inline-6 CDI that took over the flagship 6-cylinder diesel role, sitting above the OM654 in the hierarchy for heavier chassis applications.
FAQ
Mercedes-Benz OM654Frequently Asked Questions
Question 1How much does a Mercedes OM654 engine replacement cost-
A reconditioned Mercedes OM654 engine typically costs between £3,000 and £5,000 for supply only . Fitted costs generally range from £3,520 to £5,780 depending on the specialist, while used units can be found from £1,800 but carry higher risk due to the complexity of the emissions systems. Compare OM654 engine replacement quotes today
Compare OM654.920/921 quotesQuestion 2What is the most common failure on the OM654 engine-
The most documented issues are AdBlue system faults, EGR cooler leaks, and occasional timing chain wear. AdBlue dosing module or NOx sensor failures trigger limp mode, while EGR cooler cracks can lead to unexplained coolant loss and white smoke from the exhaust. Get quotes for a rebuilt OM654 with these issues resolved
Compare OM654.920/921 quotesQuestion 3Which Mercedes models use the OM654 engine-
The OM654.920 and .921 were fitted to the W205 C-Class (C 200 d, C 220 d), the W213 E-Class (E 200 d, E 220 d), and the X253 GLC-Class (GLC 200 d, GLC 220 d), serving as the definitive modern 4-cylinder diesel for these chassis between 2016 and 2023. Check your registration to confirm your exact OM654 fitment
Compare OM654.920/921 quotesQuestion 4Should I buy a used or reconditioned OM654 engine-
A reconditioned OM654 is strongly recommended over a used unit. A proper rebuild will proactively address the common failure points by verifying the AdBlue dosing module, replacing the EGR cooler, and refreshing all critical seals, whereas a used engine with unknown history risks hidden emissions system faults. Compare reconditioned OM654 engine prices from UK specialists
Compare OM654.920/921 quotesQuestion 5How do I know if my car has the OM654 and not the OM651 or OM656-
The OM654 is a distinct 2.0L modular common-rail diesel, producing a unique sound and performance profile compared to the older 2.1L OM651 or the larger 3.0L OM656. The engine code is stamped on the right-hand side of the cylinder block near the oil filter housing and is also listed on your V5C logbook. Enter your reg above to identify your exact engine code ═══════════════════════════════════════
Compare OM654.920/921 quotesCompare Mercedes-Benz OM654 Engine Prices Today
Vetted UK specialists who work on modern Mercedes CDI systems like the OM654 every week Minimum 12-month warranty on every reconditioned and rebuilt OM654 engine Nationwide delivery - supply-only or full supply & fit available across the UK Get a free, no-obligation comparison of OM654 engine prices tailored to your exact vehicle. Our registration lookup confirms your fitment before any quotes are sent, ensuring you receive the correct unit with verified AdBlue and EGR components. With reconditioned OM654 engines starting from £3,000, comparing takes two minutes and could save you hundreds on labour and unexpected teardowns.
Vetted UK Specialists
Vetted UK specialists for OM654.920/921 replacements
Minimum 12-Month Warranty
Minimum 12-month warranty on reconditioned and rebuilt options
Nationwide Delivery
Nationwide delivery plus supply and fit availability
Expert Support
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