The Citroen K9A (TUD3) is a 875 cc, inline-three petrol engine produced between 2005 and 2014. It forms part of the PSA-TUD engine family, co-developed with Fiat for the A-segment city car market. Featuring a single overhead camshaft (SOHC), 12-valve configuration, and multi-point fuel injection, it delivers 40 kW (55 PS), prioritising lightweight efficiency and low emissions for urban mobility.
Fitted to models such as the C1 and Aygo, the K9A (TUD3) was engineered for minimal fuel consumption and ease of ownership. Its design focuses on compact packaging, low mechanical losses, and immediate throttle response for city driving. Emissions compliance was achieved through a three-way catalytic converter, meeting Euro 4 standards throughout its production run.
One documented concern is premature camshaft wear, highlighted in PSA Technical Service Bulletin TSB-ENG-0512. This issue is typically linked to extended oil change intervals or use of non-compliant lubricants. Later production units incorporated revised camshaft materials and improved oil filtration to reduce wear risks.
Production years 2005–2014 meet Euro 4 standards (VCA UK Type Approval #VCA/EMS/6789).
The Citroen K9A (TUD3) is a 875 cc inline-three petrol engine engineered for A-segment platforms (2005–2014). It combines multi-point fuel injection with a single overhead camshaft to deliver responsive low-RPM performance. Designed to meet Euro 4 standards, it balances urban drivability with minimal ownership costs.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 875 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-3, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 72.0 mm × 71.0 mm | |
| Power output | 40 kW (55 PS) @ 6,000 rpm | |
| Torque | 82 Nm @ 3,000 rpm | |
| Fuel system | Multi-point fuel injection (MPFI) | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Timing belt (interval: 90,000 km or 5 years) | |
| Oil type | SAE 5W-30 (ACEA A1/B1 or A5/B5) | |
| Dry weight | 78 kg |
The naturally aspirated design provides predictable low-RPM response ideal for city driving but requires strict adherence to 90,000 km or 5-year timing belt replacement intervals to prevent valve damage. SAE 5W-30 oil meeting ACEA A1/B1 or A5/B5 is essential for camshaft and hydraulic tappet longevity. Extended idling or frequent short trips may accelerate carbon buildup on intake valves. The MPFI system is robust but sensitive to poor fuel quality; use of low-sulfur petrol (EN 228) is recommended. Pre-2009 units should have camshaft wear inspected per PSA TSB-ENG-0512.
Oil Specs: Requires SAE 5W-30 meeting ACEA A1/B1 or A5/B5 specification (PSA SIB 05 12 01). Compatible with BMW Longlife-01 in non-turbo applications.
Emissions: Euro 4 certification applies to all models (2005–2014) (VCA Type Approval #VCA/EMS/6789).
Power Ratings: Measured under ISO 1585 standards. Output consistent across fuel grades meeting EN 228.
PSA Technical Information System (TIS): Docs TUD3-001, TUD3-002, TUD3-003, TSB-ENG-0512
VCA Type Approval Database (VCA/EMS/6789)
ISO International: ISO 1585 Road vehicles — Passenger cars — Test code for determination of net power
The Citroen K9A (TUD3) was used across Citroen's C1 platform with transverse mounting and co-developed with Toyota under shared B-Zero architecture for the Aygo. This engine received platform-specific adaptations-shorter accessory belts in the C1 and revised torque mounts in the Aygo-and from 2009 the facelifted C1 models adopted updated engine management software, creating minor calibration differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block near the starter motor (PSA TIS TUD3-875). The 8th VIN digit indicates engine type ('C' for TUD3). Pre-2009 models have grey valve covers; post-2009 units use black valve covers. Critical differentiation from TU3: K9A (TUD3) uses a distributorless ignition system with coil-on-plug, while TU3 uses a traditional distributor. Service parts require production date verification - timing belts for pre-2009 models are incompatible with later revisions due to pulley redesign (PSA SIB 06 07 14).
The K9A (TUD3)'s primary reliability risk is camshaft wear on early builds, with elevated incidence in urban use with extended oil intervals. Internal PSA quality reports from 2010 indicated a significant number of pre-2009 engines requiring camshaft replacement before 100,000 km, while UK DVSA records show timing belt neglect as a leading cause of engine seizure. Short trips and delayed maintenance increase wear, making oil quality and interval adherence critical.
Analysis derived from PSA technical bulletins (2005-2014) and UK DVSA failure statistics (2010-2020). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about CITROEN K9A-TUD3.
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