BimmerFest BMW Forum banner
1 - 9 of 9 Posts

·
Registered
Joined
·
81 Posts
Discussion Starter · #1 ·
So my service engine light is very interesting. It has come on and off again 4 times over the past two weeks. Two days ago it turned off and hasn't returned.

What might cause it to sporadically turn on and off like this (other than loose gas cap)? Of course I say that and who knows - maybe I have a broken or bad gas cap???

Are the error codes stored even after the light goes off? Crappy gas? My bad attitude?

I know the light is related to emissions and I'm not too worried about it. I just find it a bit unhelpful that a light that says "service engine soon" can turn on and off 'randomly'. Might as well read "time to visit the stealer" if it's going to act like that.

My car goes in on Tuesday to move on to expansion tank #3 and if the codes get stored at least I could have them read it to see what might be going on?
 

·
Registered
Joined
·
1,279 Posts
Sounds like you have a sensor that's failing. There may or may not be codes stored. You should have them read.

Even if you're not concerned about emissions, it might be something that will damage something else if it's not fixed. For example, if you have an oxygen sensor failing, it might cause the fuel mixture to be rich and that will eventually damage the catalytic converter.
 

·
Registered
Joined
·
81 Posts
Discussion Starter · #3 ·
Well, hopefully they can pull the codes for me. At this point the light is still off - pretty strange.
 

·
Registered
Joined
·
23 Posts
I've had something similar happen to me, where my SES light would randomly go on/off. I never had any "problems" power wise, nor did it feel any different driving. It was at a point where it would come on and after 150 miles turn off, but the next time would come back on and after 80 miles turn off. Completely random IMO. It did this probably 5x over a 6month period.

I then had Autozone pull the codes and it came back with a P0171 code. But literally leaving the Autozone parking lot heading home, it would then turn off not come on for 4-5 fillups. After the last time it came back on I finally brought it to the dealer, where the results were my MAF sensor being the culprit.

I went ahead and cleaned it and it's been 3 months and the SES light hasn't returned. Like others who have done the cleaning, I noticed an increase in mpg. I figured before dropping the $$ on a new MAF I'd try the cleaning first and so far so good (knock on wood). Just my $.02
 

·
I'm otay. You are not.
Joined
·
1,337 Posts
Mine does the intermittent on/off every so often. Most of the time, there are no codes stored; I've had a couple of times where it pointed to my thermostat (sticking open). It's never affected driveability (performance or otherwise), so I've not bothered with it. I did just replace the MAF last week. The car started needing three cranks to run after stalling on the first two, but only after it was warmed up. It didn't do that when you disconnected the MAF. I cleaned it, and that worked for two days. I'm over 90K and figured I'd just as soon replace it. So I did. I'll see how the SES light does now and repost after a couple of months.
 

·
Registered
Joined
·
7,781 Posts
I've had something similar happen to me, where my SES light would randomly go on/off. I never had any "problems" power wise, nor did it feel any different driving. It was at a point where it would come on and after 150 miles turn off, but the next time would come back on and after 80 miles turn off. Completely random IMO. It did this probably 5x over a 6month period.

I then had Autozone pull the codes and it came back with a P0171 code. But literally leaving the Autozone parking lot heading home, it would then turn off not come on for 4-5 fillups. After the last time it came back on I finally brought it to the dealer, where the results were my MAF sensor being the culprit.

I went ahead and cleaned it and it's been 3 months and the SES light hasn't returned. Like others who have done the cleaning, I noticed an increase in mpg. I figured before dropping the $$ on a new MAF I'd try the cleaning first and so far so good (knock on wood). Just my $.02
Similar here. Mine only went on once and the code reader came up with P0171 (MAF). Reset the light and it didn't come back on, but they're known for going bad over time and rather than wait and possibly do damage to my cats, a couple of weeks later I replaced it with the Range Rover MAF for about $150. That was close to a year ago and no light since.
 

·
Registered
Joined
·
348 Posts
Mine came on and off for awhile - ended up being a coil pack going bad. I think the lesson here is to have the stored code read (if there is one) and regardless of whether the light has turned itself off, consider replacing whatever is the source of the fault. Preventative maintenance is always cheaper than cleaning up the mess after a failure. My .02
 

·
Registered
Joined
·
81 Posts
Discussion Starter · #8 ·
Thanks for the advice. Goes into the shop tomorrow to get the expansion tank fixed. Hopefully these guys can read/understand the codes so I don't have to make another trip.

Front left tire blew today. But that's turning into a good thing. 18" are going on today!!!
 

·
I'm otay. You are not.
Joined
·
1,337 Posts
I have an update... way sooner than I thought. :banghead: The SES light came back on, the three times a charm starting is back when warm, and the codes are now for an o2 and the cam position sensor. I'll drive it til the light comes back on and hopefully the o2 light was MAF related and I'll just need a cam position sensor (again). And maybe I'll have a spare MAF, too!
 
1 - 9 of 9 Posts
Top