Citroën C5 X
The EP6DT/EP6CDT (Prince THP) is the most problematic engine from the PSA-BMW cooperation. Timing chain wear, high oil consumption, and VVT solenoid failures occurred on a large scale; camshaft sprocket slipping was only resolved from 2012 with harder gears. Short oil change intervals (max. 10,000 km) and quality 5W-30 engine oils are mandatory.
Powerful C5 X petrol
181 hp in the modern C5 X — a punchy turbopetrol for the comfortable touring saloon. A harmonious and confident combination with the 8-speed automatic.
Engine Weaknesses 7
The THP engine suffered severely from timing chain stretch caused by the weak single-row tensioner, combined with camshaft sprockets slipping on the shaft. This leads to uncontrolled valve timing loss and can cause piston-to-valve contact. PSA improved the sprockets from model year 2012 onwards.
Symptoms: Rattle on start-up, power loss, rough idle, check engine light P0011/P0012, in the worst case engine damage without warning
THP engines frequently consume 1–3 litres of oil per 1,000 km from around 80,000 km, in extreme cases up to 4 l/1,000 km. Causes are worn exhaust valve stem seals and piston rings worn from soot deposits.
Symptoms: Very frequent oil top-ups, blue or white smoke from exhaust, black deposits on spark plugs, oil smell in engine bay
The THP turbocharger suffers from insufficient oil supply, especially when the oil level drops too low or the oil degrades from excessively long change intervals. Oil coke from the crankcase also blocks the oil feed line to the turbo.
Symptoms: Whistling or rattling turbo noise, blue smoke under full load, power drop, measurable boost pressure loss
The high-pressure fuel pump (HPFP) on the EP6 THP fails frequently and results in insufficient fuel rail pressure. The engine stumbles on cold start or under load. Part number 1920LL (THP 150) or 1920RT (THP 200).
Symptoms: Stumbling on cold start, fault code P0087 fuel pressure too low, power loss under full load, hesitant throttle response on acceleration
In the EP6 THP, a secondary chain drives the oil pump. This secondary chain wears and can break. The result is a drastic drop in oil pressure that causes immediate engine damage if the STOP warning is ignored.
Symptoms: Oil pressure warning light (STOP), pressure drop despite correct oil level, metallic noises, in the worst case engine shutdown
Direct injection without intake valve wash, combined with EGR recirculation, promotes soot deposits on the intake valves. In PHEV use with frequent electric driving, cold start condensation can make the problem worse.
Symptoms: Rough idle, starting difficulties when cold, engine stumbling, power loss
The wastegate control system on the EP6 THP is vacuum-operated with inverted logic. The solenoid valve for the vacuum supply fails frequently, leaving the wastegate open and preventing any boost pressure from building.
Symptoms: Vehicle only accelerates weakly as if naturally aspirated, maximum speed limited to 100–110 km/h, no turbo boost felt, fault code P0299
Vehicle Weaknesses 4
Stellantis recalled the C5 X PHEV due to potential fire risk from faulty high-voltage battery cells. Affects plug-in hybrid variants produced between 2022–2023. A battery management software update was applied.
Owners of early C5 X build years report immature electronics: the infotainment system freezes or reboots, and the radio has cold dropouts in the first few minutes of driving. Citroën has not delivered immediate software solutions for all problems.
The 8-speed EAT8 automatic in the C5 X shows slight shift hesitation and jolting during warm-up, especially. On early production vehicles, software bugs led to unlogged gearbox malfunctions. Citroën has partially rolled out software updates.
The C5 X is built for maximum comfort. The progressive suspension system tends towards pronounced body roll in fast corners and significant dive under heavy braking. This gives an uncertain impression dynamically, but is inherent to the design.
