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Diary of the EVAP system - BMW E92 335i

 

Have you ever gotten the dreaded "check engine" or "service engine soon" light on? Your anxiety level goes up and you start to sweat. You start thinking to yourself, "what now! What else could be going wrong with my car..." 

With your worry and frustration growing you keep on driving only to realize a mile or two down the road that the car doesn't feel any different only this dang light is on! You pull into your nearest service station and you let the staff know you have an issue with your check engine light. A technician hooks up his diagnostic scanner and tells you, "Well it appears you have an evap fault code."

What in the heck is an evap fault code?!?!

The short answer needs a little background in what an evap system is. Every vehicle rolling out today has a federally mandated emissions system built into the vehicle. The evap system is a closed system which captures any fuel vapor within your fuel system that can potentially leak out and harm the atmosphere. When your vehicle throws evap fault codes there is generally some sort of problem within the system, usually a leak somewhere. 

We here at M-Spec Performance see a lot of evap fault related codes which generally leads to a failure to pass New York State Emissions testing. Yeah the same little inspection sticker you need to get or else the meter maids will write you up an expired inspection ticket. 

The first thing we do is to determine what the code means and try to interpret that information to the best of our professional ability. We then activate the DM-TL pump which is essentially a pump that pressurizes the evap system to detect leaks. If the DM-TL pump test fails then we know we have to go a step further.

The next course of action is to find the leak. How do we do this? We then induce smoke via the fuel tank cap with a special fitting that allows us to attach our smoke machine. We would then induce smoke into the system and try to track down where that leak may be coming from. 

In the special case of the 2011 BMw 335i in question, there were no leaks detected after inspection of the entire evap system. Our next test was to check in the DM-TL pump was actually activating and working properly. After removing the DM-TL pump it was found that it was working properly. The problem was then traced to a possible control issue.

Upon further investigation and research we found that the DM-TL pump was not being activated by the engine computer (DME) and that a new software update needed to be installed. Normally this operation is a "dealer only" service however M-Spec Performance is a true dealer alternative with the latest and equivalent diagnostic equipment

After the software was updated, the DM-TL pump test was then initiated and low and behold it worked and passed with flying colors! We here at M-Spec Performance are your premiere German Car Experts. We are Queens and Brooklyn's leading service shop and dealer alternative for BMW Audi Volkswagen Mercedes Benz and Mini Cooper. Next time you have an emissions related computer fault please contact us so we can help you.

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