willimaier10
Megane Exhaust Treatment Malfunction
Summary of the thread
A 2021 Renault Megane hybrid is experiencing an "Exhaust treatment malfunction" warning, rough engine performance, and an exhaust leak. The issue may be related to the EGR valve or particulate filter, but a defective lambda sensor is identified as the cause. Replacing the lambda sensor is expected to resolve the problem, with an estimated repair cost of 375€.
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4 comment(s)
willimaier10 (community.author)
Lambda sensors, eh? I haven't looked at those specifically. Where are they located, and is there any easy way to test them without specialist equipment? I'm trying to avoid a costly workshop visit if possible!
gabrielherrmann2
They're usually located in the exhaust system, before and after the catalytic converter. Honestly, testing them properly without the right gear is tricky. Given all the symptoms you're experiencing – the light, the smell, and the rough running – it might be best to get it properly diagnosed. It could be something simple, but it could also be causing further damage if left unchecked. In my case the cost was 375€.
willimaier10 (community.author)
Thanks for the advice! I've booked it in at the local workshop. They confirmed it's a defective lambda sensor that needs replacing. Total cost will be around 375€ including labour. Hopefully, this sorts it out!
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RENAULT
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MEGANE
gabrielherrmann2
That sounds rough! I had a similar saga with my Megane. The check engine light was on, and the smell was awful. From what you're describing, it does sound like an exhaust leak. Have you checked the lambda sensors? I had a similar issue and I had to replace one of the NOx sensors as well.