2021 Peugeot 508 2.0L Diesel · ML21 UWX

On 1.5 BlueHDi (DV5) and 2.0 BlueHDi (DW10) diesel engines, the integrated AdBlue SCR tank system is a frequent failure point. The internal dosing pump, heating element, or tank pressure sensors suffer electronic faults or urea crystallization, or the tank deforms. This triggers an amber UREA warning, emissions engine fault light, and an unyielding countdown preventing engine restart once the countdown reaches zero. Rectification typically demands replacing the entire sealed plastic tank assembly, as individual pump and sensor modules cannot be serviced separately.

The fastback coupe styling of the 508 Gen 2 uses frameless side glass that must automatically drop slightly when the door handle is pulled and rise into the weatherstrip upon closing. In freezing UK winter conditions, the glass frequently freezes solid against the rubber seals, causing the anti-pinch mechanism to trigger or damaging the electric window regulator cables and plastic clips. Over time, worn or dry window seals also lead to wind buffeting, high-speed cabin whistle, and damp ingress along the door cards.

The 1.5-litre BlueHDi (DV5) diesel engine built prior to early 2023 utilizes a 7mm auxiliary timing chain linking the twin overhead camshafts, independent of the external timing belt. Due to carbon buildup and high stress, the 7mm chain prematurely stretches, slaps against the rocker housing, and can snap without warning. Chain failure throws camshaft timing out of phase, causing valves to collide with pistons and requiring cylinder head rebuilding or full engine replacement. Peugeot later engineered an upgraded 8mm chain kit with modified camshafts under safety campaigns.