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Discussion Starter #1
I have a 2001 525it which I bought in September 2008. Soon the SES light came on and I suspected tihe fuel cap and replaced it. The light went out eventually. Now I have noticed the SES light comes on when the fuel reaches half tank, and will go out a few days after I fill the tank. Dies anyone else have these symptoms?
 

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Freude am Fahren
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6,378 Posts
Sounds like it's still a vapour recovery system problem***8230; maybe leaky gas cap?
 

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Discussion Starter #3
I dunno ... I loosen and re tighten the new cap and that doesn't work. But when I fill the tank it goes out ... weird.
 

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You need to have your car scanned so that you can recover the OBD II code. The SES light comes on when a fault has been initiated by the "emissions" system. The emission system includes multiple systems under a broader umbrella.

For instance, if you get the car scanned and it comes back as an "evaporative emission system" fault code...the culprit could be more than just the gas cap (which usually comes back with a P0440 code) ...it could also include some of the others below:
  1. Evaporative canister or cracked hose
  2. Purge or vent solonoid defective
  3. Vacuum leak at engine
  4. Defective or loose fuel cap

OBD II monitors the following systems that are also considered "emissions"...and this is why you need to have the CODES scanned FIRST before asking what could be wrong...as you see...the list is long:
  • converter efficiency,
  • catalyst heater (if used),
  • evaporative system,
  • air injection system (if used),
  • fuel trim,
  • oxygen sensors,
  • exhaust gas recirculation (if used),
  • secondary air system (if used),
  • the coolant thermostat (starting in 2000),
  • positive crankcase ventilation system (starting in 2002)
  • and even some A/C systems on 2002 and newer vehicles.

Good luck...and remember that many vendors like AutoZone will read them for free. Once you get your car scanned and receive what area created the fault...and if you get the "P" codes...you can come back here...or even google "OBD II codes"...there's lots of info out there. :)

 
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