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Q: Exhaust emission light on

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So last night while driving there was a drop in power that I could feel, I drove it home slowly, in the morning it was fine, but started it up now and there was something wrong with how the engine was running and now the exhaust emission light is on, turned it off and back on and it's fine now but light is still on, there is a slight noise at the bottom of my revs a bit above idol. Any ideas?

Hi, thanks for writing in. I am wondering what the model, make, and year of your car is, as well as if you have an automatic or manual transmission. This information will make our answers be more accurate. In this case I am fairly certain you are driving a diesel of some sort, but the year of the vehicle is everything for a quality answer. Diesel emissions systems were not required before 2007. They were rolled in from 2007-2010 in the US. You could be in Europe where this would be different as well as the systems may be different as well.

What I can tell you is the catalyst reduction systems on modern diesel motors are highly complicated. The loss of power you are experiencing is most likely due to the PCM (powertrain control module) going into a limp mode. Emissions in this case is not likely something that will hurt your motor. But the manufacturers are being forced to reduce power to force people to get these systems fixed. Something to do with climate change. The EPA in the US is taking this very seriously.

Whatever is wrong is still wrong. Emissions systems on your must make many different changes based on a great many factors. Driving at a cruise, cold start up, hauling a heavy load, going up a long hill, start up after it sat at the grocery store and on an on are all different to your emissions system. For this reason you will experience a myriad of strange symptoms.

You car needs to be diagnosed by someone with experience with diesel emissions systems. Since these systems are new, this likely means a dealership or an independent shop that specializes in diesels. Most independent shop will not have had much time with these systems as of yet.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

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