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#1
09-15-2006, 01:12 PM
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2000 S430 W220 Fuel Tank Open Check Filler Cap?
Today, when I was driving, all of a sudden the message Fuel Tank Open Check Filler cap came on... I checked the cap and seems to be tight. Is the fuel cap the possible source? Or could it be something else?
I checked it with an OBDII scanner, and I think it shows P0455, P0170, P0173... something like that... Please advise... 
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#2
09-15-2006, 01:42 PM
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170 and 173 are part load adaptations at limit. consistent with a vacuum leak but usually seen with a bad air mass sensor. keep us posted what you find, look for air leaks.
__________________
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#3
09-16-2006, 12:03 AM
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Hmmm... air leaks? vaccum leaks? let me check those... but could there be anything that will leak in the fuel tank? like sensor or stuff like that?
This afternoon when I was driving the car, it was about 78 degrees and the tank is about 3/4 full... the message came on after about 15 minutes of drive... I reset the OBDII code, and tonight about 65 degrees, the message hasn't popped up at all during about an hour of drive. Could temperature have something to do with it? Or could it be something else? How do I check for vaccum leaks on a W220? Anyone has a vaccum diagram? Please help! Thanks!
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#4
09-16-2006, 03:34 PM
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The P0170/173 are the codes that usually indicate a faulty MAF sensor, the P0455 is the code that prompted the message about the fuel filler cap. Obviously, check the gas cap first. Some other things that can cause the P0455 code are, in no particular order, the purge valve, fuel tank pressure sensor, and the charcoal canister shut-off valve. It's an easy system to troubleshoot if you have a hand vacuum pump and an SDS, OR some other means of activating the shut-off valve.
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#5
09-17-2006, 09:17 AM
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Thank you so much for the advice!
Would a faulty gas cap cause p170/173 codes? Or is that solely and separately caused by the MAF Sensor? Does the gas cap fail often? Has anyone replaced their gas caps? Also, I do have a vaccum tool, how do I go about diagnosing the system? Any hints? Once again, thanks for all of your great help  Oh btw, is there any cheap alternative to the SDS? I know the dealer ones are costly, but is there a simplied version or cheaper version for DIYers?
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