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…
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 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.
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.
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The DW12ME5 is generally reliable when maintained properly. Its common-rail design and proven architecture make it durable, but critical attention must be paid to the 120,000 km timing belt interval and fuel quality. HPFP failure is common on pre-2009 units. With timely servicing and use of correct oil (5W-30), these engines regularly exceed 200,000 km.
The most documented issues are high-pressure fuel pump failure due to wear, timing belt failure from missed services, and DPF clogging from short trips. These are addressed in PSA service bulletins, particularly SIB-ENG-2009-07. EGR fouling is also seen in high-mileage urban examples. Post-2009 models feature improved pump lubrication and reliability.
The DW12ME5 was used in the Citroën C5 (2.2 HDi 136), C6 (2.2 HDi 136), and Relay (2.2 HDi 136) from 2005 to 2015. It was also shared with Peugeot (407 2.2 HDi 136, 807 2.2 HDi 136) under the DW engine family. All applications are front-wheel drive with longitudinal engine mounting.
Yes. The DW12ME5 responds well to ECU remapping, with stage 1 tunes typically gaining +25–35 kW. The Bosch common-rail system and Garrett turbo support moderate increases. Supporting mods (upgraded intercooler, exhaust) are recommended for sustained performance. However, over-tuning can accelerate HPFP and DPF issues, so conservative maps are advised.
In combined driving, expect 6.0–7.0 L/100 km (40–47 mpg UK). Real-world consumption is excellent in mixed driving (~6.5 L/100km), but urban use with DPF regeneration can exceed 8.0 L/100km. Highway efficiency improves to ~5.5 L/100km (51 mpg UK). Fuel quality and driving style significantly impact economy.
Yes. The DW12ME5 is an interference engine. If the timing belt fails or jumps, piston-to-valve contact will occur, causing catastrophic internal damage. Given the 120,000 km service interval, proactive replacement of the belt, tensioner, and water pump is essential to avoid expensive repairs.
PSA specifies Total Rubia TIR 5W-30 (or equivalent meeting PSA B71 2300). This low-SAPS oil is essential for DPF and SCR system longevity. Oil must be changed every 15,000 km or annually to maintain lubrication and prevent soot buildup, especially in mixed driving conditions.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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