Diesel car owners are facing a strange problem with PUC checks in India

Most of the time when I take either of my 2 diesel vehicles (Audi A4 or BMW X1) for an emission check, there's some error related to RPMs.

BHPian dinu2506 recently shared this with other enthusiasts.

Dear friends,

I keep getting this issue each time I go for emission checking for my 2016 Audi A4 Diesel 35 TDI and my 2013 BMW X1 sDrive 20D, both BS4. It's a pain when the sensor does not give proper readings. They keep experimenting at various locations on the engine bay and sometimes it works. Last time I took a photo of where it worked. It was on one of the alternator mounting bolts.

Today, I had the same issue and made him use the same place, but this time it did not work. Removed the engine cover and tried on the top of the injectors (where it works for my BMW x1). Went to two different places to no avail.

Mostly, the error is that the rpm is not within limits. On top of it, they give gyan like BMW and Audi do not emit much smoke to detect, the car generates too much horsepower, etc etc. And this is not recent, it has always been a pain from the time it was new. Getting fed up now.

I'm assuming this is faced by many. Any help on this matter will be appreciated for both the Audi and BMW diesels.

Here's what BHPian vinay.sathyan had to say about the matter:

I really thought I was the only one facing this problem, mine is a GLC220d.

Firstly, finding diesel emission test centers is difficult enough and then this.

My first experience was horrible, he was raising the rpm on the car so much since he was not getting any reading and I felt horrible seeing that happen to my car.

Also, if it helps, this is a list of diesel pollution testing centers I noted in Bangalore, some are verified some are not. Please call ahead and then visit.

Here's what BHPian condor had to say about the matter:

I face a similar issue on my 2013 Safari Storme. This has happened at the same testing centre at least twice in a row now, and I need to idle and run the engine for at least 10 minutes before the test comes out successful. The issue was not there earlier, which was done at other testing centres. Hence plan to go to a different place next time.

However, if any suggestions to avoid this are posted, would be happy to try them out.

Here's what BHPian kiran_cr had to say about the matter:

I too got PUC checked for my Innova Crysta 2.8Z yesterday. The RPM sensor lead was just placed on the engine casing just below the engine cover. Test was done only with RPM values and not tailpipe exhaust.

When I enquired with the person, he mentioned that the current regulation for Diesel vehicles mandates only an RPM test and exhaust is not required. Apparently, they can check if the vehicle's pollutants are within range or not based on the engine vibration and rpm. I'm not sure of the technicalities here, can anyone throw light on this topic, please?

Here's what BHPian Jeroen had to say about the matter:

There is absolutely NO WAY to measure anything in the exhaust gasses in the engine bay. You need something in the exhaust pipe to measure the exhaust gasses. It is not just the engine but also the proper functioning of the catalytic converter that gets measured this way.

Whatever they attach inside the engine bay is just some pick up device for the RPM. But RPMs don’t and can’t tell you anything about what spews out of your exhaust pipe.

In some countries, the MOT is done without the exhaust check on modern cars. As long as your Check Engine Light doesn’t come on it is considered fine.

Check out BHPian comments for more insights and information.