The Citroën 4HK (DW12ME5) is a 2,179 cc, inline-four turbocharged diesel engine produced between 2005 and 2015. It belongs to the PSA DW12 engine family, co-developed with Ford for longitudinal mounting in executive and commercial vehicles. Featuring a cast-iron block, aluminium head, and common-rail direct injection, it delivers strong torque and smooth refinement. In standard tune, it produces 100 kW (136 PS) and 340 Nm of torque.
Fitted to models such as the Citroën C5, C6, and Relay, as well as the Peugeot 407 and 807, the DW12ME5 was engineered for long-distance comfort and fleet durability. Emissions compliance was achieved through exhaust gas recirculation (EGR), diesel particulate filter (DPF), and selective catalytic reduction (SCR) with AdBlue injection, meeting Euro 4 and later Euro 5 standards.
One documented concern is high-pressure fuel pump (HPFP) internal wear due to lubrication limitations, particularly in high-mileage or poorly maintained units. This issue, highlighted in PSA Service Bulletin SIB-ENG-2009-07, can lead to hard starting, power loss, and engine shutdown. From 2009, revised lubrication pathways and updated pump calibration were introduced to improve longevity in later production runs.
Production years 2005–2009 meet Euro 4 standards; 2010–2015 models comply with Euro 5 (VCA UK Type Approval #VCA/EMS/9345).
The Citroën 4HK (DW12ME5) is a 2,179 cc inline-four turbocharged diesel engine designed for executive and commercial vehicles (2005–2015). It combines common-rail injection with a variable geometry turbocharger to deliver responsive torque and improved efficiency. Designed to meet Euro 4 and Euro 5 standards, it balances performance with emissions compliance and long-term reliability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,179 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 85.0 mm × 96.0 mm | |
| Power output | 100 kW (136 PS) @ 4,000 rpm | |
| Torque | 340 Nm @ 2,000 rpm | |
| Fuel system | Bosch CRS 2-25 common-rail (up to 1,800 bar) | |
| Emissions standard | Euro 4 (2005–2009); Euro 5 (2010–2015) | |
| Compression ratio | 16.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Garrett VNT28 variable geometry turbo | |
| Timing system | Rubber timing belt (interval: 120,000 km or 8 years) | |
| Oil type | Total Rubia TIR 5W-30 | |
| Dry weight | 172 kg |
The variable geometry turbo provides strong mid-range torque ideal for motorway cruising but requires adherence to 120,000 km timing belt intervals to prevent valve/piston contact. Total Rubia TIR 5W-30 oil is essential due to its low-SAPS formulation and compatibility with DPF/SCR systems. The Bosch HPFP demands ultra-low-sulfur diesel (EN 590) to prevent internal wear; contaminated fuel accelerates pump failure. SCR AdBlue injection reduces NOx emissions but requires periodic refilling. Post-2009 models feature revised fuel pump lubrication and enhanced EGR cooling, improving reliability. Cold-start idling should be minimized to reduce EGR soot buildup.
Oil Specs: Requires Total Rubia TIR 5W-30 or equivalent meeting PSA B71 2300. Supersedes ACEA C3.
Emissions: Euro 4 applies to 2005–2009 models; Euro 5 certification confirmed for 2010–2015 (VCA Type Approval #VCA/EMS/9345).
Power Ratings: Measured under ECE R85 standards. Output requires EN 590 diesel for optimal injection performance (PSA TIS DW-ENG-09).
PSA Technical Information System (TIS): Docs DW-ENG-06, DW-ENG-07, SIB-ENG-2009-07
VCA Type Approval Database (VCA/EMS/9345)
ISO 8854: Road vehicles — European emissions standards
The Citroën 4HK (DW12ME5) was used across Citroën's D-segment platforms with longitudinal mounting and shared with Peugeot under the DW engine program. This engine received platform-specific calibrations-adapted EGR flow in the C6 and revised SCR injection logic in the Relay-and from 2009 the facelifted C5 II adopted updated fuel pump lubrication and ECU mapping, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block near the exhaust manifold (PSA TIS DW-ENG-10). The 8th VIN digit indicates engine type ('M' for DW12ME5). Pre-2009 models have silver injector bodies; post-2009 units feature updated pump lubrication. Critical differentiation: DW12ME5 uses a Bosch CRS 2-25 common-rail system with SCR AdBlue injection, while the earlier DW12TED4 uses a Delphi system without SCR. Service parts require model-year verification—fuel pumps and ECUs from pre- and post-2009 builds are not interchangeable (PSA SIB-ENG-2009-07).
The DW12ME5's primary reliability risk is high-pressure fuel pump failure on high-mileage or poorly maintained units, with elevated incidence in stop-start urban use. PSA internal quality reports from 2011 indicated a significant number of pre-2009 units requiring HPFP replacement before 150,000 km, while UK DVSA MOT records show increased emissions-related failures in short-trip examples. Extended service intervals and low-quality fuel accelerate degradation, making service adherence and fuel quality critical.
Analysis derived from PSA technical bulletins (2009–2015) and UK DVSA failure statistics (2012–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about CITROEN 4HK-DW12ME5.
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