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check engine lamp

734 Views 6 Replies 4 Participants Last post by  ytqm
my CEL has been on for a few weeks on my 2001, 1.8t automatic.
Now, i'm a BMW technician, and come across this stuff on a day to day basis, but,,,, i dont have a VW scantool.
I borrowed a friends MAC tools scanner, he didnt have VW software, but he has obd2 generic software.
my fault code is for mixture to lean.
i tried going on the datastream to look at my o2 sensors, but the damn tester only shows one 02, and i dont know which one it is. the voltage on this one o2 hangs out around .6 volts, which would be fine if it was the sensor after the cat. but if its the before cat sensor, this is a bad reading. i'm pulling my hair out because this tester sucks. why would it only show one 02 sensor???
Whats the most common one to go bad first, the after or before cat sensor??
my car has 75k on the clock, so it wouldnt hurt to get them both, but i dont wanna fix what aint broke.
any ideas??
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My CEL comes on when I dont tighten up my gas cap tight enough!

Weird, YES, but it "could" be a problem!!!

Rich :wink:

Mybe your car dont like you cause you a BMW tech! :lol:
ha ha.
no really, the loose cap would only cause a tank system leakage fault.
Yeah you should know, but if my CEL if off, and my gas cap is not tight enough, then my CEL will come on!!!

Rich :wink:

PS I doubt this is your problem, but I just thought I would throw in the weirdest possible problem!
not a wierd problem, man. almost all cars now will put the cel on when the cap is loose.
its an emmisions thing, the epa wants to keep fuel vapors in the fuel tank
Where are you located? Have you checked the Information Forum "VAG-COM Locator" thread to see if there is someone in your area with a Vag-com who can help you out with the scan?

Also, when my car gave mixture-too-lean faults it turned out to be a leaky vacuum line. I would guess that a bad MAF sensor is a more common fault than a bad O2 sensor. I don't know which O2 sensor is more prone to failure, but, at least with the info that you've posted, I'm doubtful that either is causing your problem.

Good Luck.
Its the MAF. Longterm trim ...too lean, if you have under 70k on the car it should be covered under an extended warranty on that part.
1 - 7 of 7 Posts
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