# 2009 X5 Diesel Service Engine Light



## href9 (May 28, 2013)

Greetings! First time poster but have used this forum for quality information for my 09 X5.

Anyway, my SES light came on about two months ago and then went off after I refueled. I chalked it up to bad fuel. The same thing happened about two weeks after that and again, it went off after I refueled. Again, about two weeks later the light came on and has been a constant since then. I ran the OBD code and it came back as P21A8. I've checked online as well as this forum, with only one hit on here that hints at the DEF tank. Has anybody else ever ran into this? I called the dealer and they say they can't cross reference to a 'P' code, which I'm sure is crap.

Any help would be appreciated!


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## Flyingman (Sep 13, 2009)

I don't see the connection with your fuel tank and the DEF.

I've seen my SES go off after refilling, but it goes away shortly after. I suspect they monitor that the fuel cap is tight, perhaps to control emissions or evaporation like a gasoline tank.

I would double check that your cap is indeed tight. That's an easy one.

I'll look for your code and see what it might be. Sounds like a nuisance code to me, one that probably is not anything significant going wrong. It's resetting on it's own and you don't have to go to the dealer to reset it.

I have a Garmin EcoRoute HD which reads all the SES codes live while I drive and I can reset a nuisance code using my Garmin. A $99 investment, good to know information and avoids unecessary visits to the dealer just to reset an SES light.


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## href9 (May 28, 2013)

Flyingman said:


> I don't see the connection with your fuel tank and the DEF.
> 
> I've seen my SES go off after refilling, but it goes away shortly after. I suspect they monitor that the fuel cap is tight, perhaps to control emissions or evaporation like a gasoline tank.
> 
> ...


After messaging the member who had the same code I did on his 335 and it turned out to be a limit switch in his SCR tank and it was replaced under warranty.

With that in mind, I was due oil change, so I did that and filled my DEF while I was there. The light reset itself and has been off ever since. Only thing I can think of is the upper limit switch is starting to fail or since the passive tank was about 3 gallons low, was getting a false indication of some kind. Either way, I will monitor it and see how it goes from there.


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