blech! limp mode woes continue..

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Aug 24, 2003 | 09:03 PM

TRM

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blech! limp mode woes continue..

a couple of links...

ok...

i've been experiencing limp mode after long hot drives. usually on a consistent basis.

so i get a CEL also. turns out it is an 17880 - EVAP LEAK DETECTION PUMP, SHORT CIRCUIT. we clear codes and go about our business. code comes back but no CEL. for this DTC i've inspected all of the fuel lines to and from the fuel tank - can't seem to find a problem, hoses clean, no crimps...unless possibly there is something with a blockage?

with regards to limp mode:

i removed and inspected TBB for cracks, splits etc. - CLEAN
i swap in 710N DV's, OE DV's looked fine.
i inspected all of the boost hoses and IC hoses - no looseness or holes.

so i give up...still getting limp mode after all the inspections and swaps.

wonder if there's something that could trip limp mode after a long hot drive in this humid/hot weather?

any clues?

would a VAG be able to dig a little deeper into the limp mode occurance?<ul><li><a href="https://forums.audiworld.com/s4/msgs/1367393.phtml">https://forums.audiworld.com/s4/msgs/1367393.phtml</a</li></ul>

Aug 24, 2003 | 09:08 PM

Audi2ptzero

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Most of the time a "short to ground"

will mean you have a blown fuse. Try running the car and using a test light to see if all the fuses are powered up.

Aug 25, 2003 | 04:53 AM

~~ModifiedA4~~

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maybe the leak detection pump is shot?????????

Aug 25, 2003 | 11:42 AM

E Vader

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I am having the same problem.......

.....I replaced the EVAP cannister, ingniton coordinator, N75, and both O2 sensors to no consequence. I checked all the fuses and none are blown.

Does the A4 have any engine compartment fuses? I don't see them listed in the Bently manual.

After multiple diagnostics, outlined by the Bently, I was instructed to run a voltmeter across the MAF and got only 2.72v. Spec says it is supposed to be 9-14.5v. Apparently the MAF, EVAP, both O2's and the N75 run off the same bulk wiring harness. I ended up purchasing a used harness (not cheap), still in the mail, will let you know if that solves my issue.

I ran multiple tests with my VAG and it just tells me that the MAF voltage signlal is too low. The MAF operates fine both at WOT and idle, sitting still (no boost), that is why I went the way of the harness. I don't get limp mode as long as I drive the car under 5psi. The gas mileage sucks because the MAF is not getting the signal right.

Let me know if you solve your issue we may have a similar culprit.

Aug 25, 2003 | 02:22 PM

Audi2ptzero

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Did you check the fuses while the car was running?

Because the harness that supplies power to the MAF, EVAP, smog pump (dbw only), 02 sensors and the N75 valve is powered up only while the car is running. There are 3 fuses that are powered up by the ecu while the car is running and should be marked as ECU or Motor but you might want to just check you manual. I had the same issue on my 2000 for 1 full month till I found the blown fuse while checking each fuse while the car was running and only got power on 1 side of that bad fuse.

Aug 25, 2003 | 02:59 PM

E Vader

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Which fuse?

I have a non-DBW. Regardless, I checked the manual for realted fuses and did not see any relevant ones.

Yeah, the car was on and running.

I will double check all fuses at the driverss side panel. Some cars have engine bay fuses/relays and that was my comment.....I don't know that we have any. Do we?