Peugeot 208 MY2021 1.5BlueHdi – Adblue / SCR fix to stop immobilization until repairs

Peugeot 208 MY2021 1.5BlueHdi – Adblue / SCR fix to stop immobilization

If you are the happy owner of a Peugeot or Citroen car equipped with a 1.5BlueHdi engine for long enough, you get to enjoy its blessings, given by the manufacturer. This diesel engine was developed with a 16valve head and much more modern technology compared to the older -but much more reliable- 8valve DV4 and DV6 engines.

Its first blessing is the timing chain. Which can snap at any time between 80.000km to 120.000km, bringing 16 bent valves and whatever else comes with it. Thankfully this can be remedied by replacing the timing chain set, to a newer stronger (thicker) 8mm type developed by Peugeot. If you are lucky enough to have a rattling chain within the first 2 years of your cars life, usually under warranty.

Its second blessing is the adblue / SCR additive system. Like with all other modern diesel engines, it was a new system developed to help bring Euro6 emissions. It is a little tank, a little pump, a little feed line and a little injector spraying Urea (yes it literally smells like pee) into your downpipe before your cat converters. How often? Every now and then but not too often. Just enough to show lower emissions in a Euro6 test cycle. To help trap and clean the extra harmful particles that the dpf filter cannot take care of.

With this lovely new system came radical, never seen before countermeasures in case it stops working. Whether it be a malfunction or just lack of Urea in your tank the result is the same: big warnings on your dashboard with a blinking Urea light. And a countdown for topping up or fixing the system before the car never starts again. I repeat: never start again!

In all of automotive history there had never been a time when a car threatened its driver it would not start unless fixed. Until now. All this for a subsystem that is not directly related to the engine’s health. These punishing countermeasures are clearly bringing the car world into a very bad, dystopian future when cars get to decide under which conditions they will work or not.

How the system works

Lets split the SCR additive system into subcomponents. Then it becomes more obvious how many different secondary problems can make your car not start. Which have nothing to do with the engine’s health by itself, just the SCR/Adblue system not working properly. Dragging everything else down with it and eventually making the car undrivable.

1. Urea tank, pump and electronic controller, that checks tank level and feed pressure to the injector
2. Feed line, from the tank which is near the back of the car, feeding urea to the injector which is at the front of the engine
3. Urea Injector , located onto the downpipe, right after the turbo, before the SCR cat and dpf filter
4. SCR cat converter inside the downpipe, right after the injector, before the DPF filter

System Diagram

[ Diesel Engine ] produces exhaust gas

[ AdBlue / SCR Injector ]  fed by the [ SCR/adblue Tank ]  = sprays Urea into the exhaust gas stream

[ SCR Catalyst (Converts NOx to N2 & H2O first)] = combines Urea and exhaust gas to produce N2 and water

[ Particulate Filter (DPF/FAP)] = Captures final soot particles, removes and burns soot during regeneration

[ Exhaust Tailpipe] = Emits harmless Nitrogen & Water Vapor

Related fault codes on the ECU

If any of the above starts malfunctioning or misbehaving, you will most likely start seeing faults like P20EE , P20E8

Reasons for the problems

These faults usually mean your AdBlue/SCR system is failing to reduce nitrogen oxides, often caused by a crystallized AdBlue injector, a crystallized feed line, a malfunctioning urea pump and tank system, or a bad NOx sensor. Whichever the problem, the engine ECU gives you a red or amber warning stating “Emission control system fault: Engine start prohibited in 1,100 km”. Or even less than that, depending on the situation. After the countdown reaches zero, the engine will no longer start and the car has to be towed to a dealership to fix the problem.

Assuming parts are available and the shop is ready to start work on the car, the ideal scenario would be to have it ready within a few days time. What happens in reality is very different to that. Due to car part shortages worldwide and all shops not keeping stock but ordering parts on the spot according to their needs, the repair takes weeks. Sometimes months.

Software Solution to Prevent AdBlue-Related Car Immobilization