# Check Engine Light ON



## Highend (Feb 28, 2004)

Hey guys, i have a 98 540i with 47k on it. Tonight I went to get gas and my Check Engine light came on. No warranty on this car so before i take it in and spend lots of $$$ i dont have i was wondering if anyone might know what it might be. The car runs fine and doesnt seem out of the norm. Only use 91 on it so i know it aint the gas.......what do you guys think it is???????????


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## JY (May 6, 2003)

Just a wild guess, did you tighten the gas cap?



Highend said:


> Hey guys, i have a 98 540i with 47k on it. Tonight I went to get gas and my Check Engine light came on. No warranty on this car so before i take it in and spend lots of $$$ i dont have i was wondering if anyone might know what it might be. The car runs fine and doesnt seem out of the norm. Only use 91 on it so i know it aint the gas.......what do you guys think it is???????????


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## marinakorp (Oct 3, 2003)

Could be MANY things... need to get the code read


If recently filled up... then it MIGHT be the gas cap

If NOT in California... then go to AUTOZONE (or some other type of BIG auto store) and get the codes read. AutoZone does it for Free. the code should be Pxxxxx x's being numeric codes... they tell what the source of the problem is


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## markseven (Apr 30, 2004)

The CHECK ENGINE light is lit on my car as well - I'll be taking it to the dealer on Saturday, I'll post their findings - this may be of help to you.


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## 540 M-Sport (Apr 23, 2004)

Could be a lot of stuff...but I would guess an O2 sensor failed.


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## marinakorp (Oct 3, 2003)

Why would that be the first guess?

Could be ... CPS sensor, MAF sensor, and a myriad of other things... just trying to get an idea of what made you jump to the o2 sensors... and which one? Which side? Pre or Post Cat Converter?


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## Mr Paddle.Shift (Dec 19, 2001)

For pre-OBDII models, that's usually the answer. But not any more with the more sophisticated OBD-II models.

But yes, an OBD-II reader is the best bet to retrieve the code.



marinakorp said:


> Why would that be the first guess?
> 
> Could be ... CPS sensor, MAF sensor, and a myriad of other things... just trying to get an idea of what made you jump to the o2 sensors... and which one? Which side? Pre or Post Cat Converter?


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## 540 M-Sport (Apr 23, 2004)

marinakorp said:


> Why would that be the first guess?
> 
> Could be ... CPS sensor, MAF sensor, and a myriad of other things... just trying to get an idea of what made you jump to the o2 sensors... and which one? Which side? Pre or Post Cat Converter?


 A wonderful "stab in the dark", as I have seen three replacements on 5 series recently, myself included... 

Please note my careful (and deliberate) use of the word "guess..."


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## AK (Jan 19, 2002)

my car has had sporadic check engine light incidents. it's always the phantom "loose gas cap" code. give it 3-4 days to see if it goes out. if it does, that was probably the issue. if it stays on, probably o2 sensors.


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## markseven (Apr 30, 2004)

My car just had the o2 sensor replaced under recall - maybe they didn't install it correctly and that's why the CHECK ENGINE light is on?

-Mark


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## dagoo98 (Apr 23, 2004)

I've seen so many people have this problem and not know why. My friend has done this about 5 times since he's gotten his e39. YOU CANNOT FILL UP THE CAR WITH GAS WHILE THE CAR IS RUNNING. This will cause the check engine light in your e39 to come on for a few days. The other people are right also, driving with the gas cap loose will also trigger the check engine light. Turn off your car when you fill up with gas.


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## Baldmtn (Apr 28, 2004)

*KEY in Ignition*



dagoo98 said:


> I've seen so many people have this problem and not know why. My friend has done this about 5 times since he's gotten his e39. YOU CANNOT FILL UP THE CAR WITH GAS WHILE THE CAR IS RUNNING. This will cause the check engine light in your e39 to come on for a few days. The other people are right also, driving with the gas cap loose will also trigger the check engine light. Turn off your car when you fill up with gas.


If you left the key in the ignition while filling up the check engine light comes on as well on some models


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## markseven (Apr 30, 2004)

My SA just called with the diagnosis: Mass Airflow Sensor. $600+... Does this sound about right for parts and labor  ?

-Mark


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## marinakorp (Oct 3, 2003)

NO



the part is about 3-400 and labor should not be 200 +


this is like putting in a light bulb on the car... not hard at all


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## markseven (Apr 30, 2004)

I'll call my SA and ask fo an itemized bill. Thanks for the info  

-Mark


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## markseven (Apr 30, 2004)

I just got my car back from Crevier and it's running great, but it was a pricey repair:

Labor - $198.24
Parts - MAF Sensor - $393.00
Tax - $30.46
Total - 621.70

Crevier charges about $115.00 per hour for labor - is this close to what other dealerships charge? :dunno: 

Luckily I have the extended warranty and no deductible...  

-Mark


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