Rain causing computer errors

I have a 2000 A6 Quattro and am finding a correlation between the weather and the functioning of my car. Currently, I am getting the following errors: ABS - Brake - Check Engine/ The ABS and Brake
lites come on and occasionally go off again. The Check Engine seems to come on and stays on. I went by my local mechanic and he reset the check engine lite once noting that I apparently had the following faults" 1. Vacuum loss in fuel system 2. Two separate faults in Oxygen sensors 3. Brake module bad
This mechanic handed me a $2000+ estimate and told me that Audi's frequently commit electronic sepuku. [his words] I'm a bit more skeptical of him than I am of Audi.
I highly doubt that all of these came into play simultaneously without lightening striking so I'm suspecting computer problems.
Note: the car was in a mild collision over the summer and the rear left fender was bent slightly... some possibility of water getting in back there.
Any thoughts?
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Are the drain holes under the windshield clear of debris? I am thinking that water fills up that tray and possibly gets some wiring wet. I have seen a few Passats with ABS modules (Blinking ABS/Brake Lights) that I could not connect to with my vag-com tool. :-( I suspect their modules need repair/replacement.
That Vacuum Loss in the fuel system has me curious though! AFAIK the fuel system is under pressure but the Emissions system can have vacuum issues. Vacuum hoses commonly need replacement on the 1.8t engines but I am not sure about the other Audi engines.
--
later,
dave
(One out of many daves)
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dave AKA vwdoc1 wrote:

My son's '98 A4 V6 has been having a few vacuum issues lately most of which we have chased down. One was tough and was associated with the secondary air pump (under passenger side and injects air into the cat during warm-up to protect it from burning out). He called the local dealer and found out that there had been a recall on the vacuum lines for the pump. The dealer has had in for a week now while they try to find the parts but at least they have supplied him with a rental car at no charge. So, in short, the V6 engines have their share of vacuum issues.
Could one of the OPs codes been due to a loose gas cap?
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fwiw, the secondary air system doesn't "protect" the cat during warm up - it adds oxygen to the cat to help burn up the excess hydrocarbons that occur during engine warm up, when the ECU is richening the fuel mix. A properly working system causes the cat to get hotter, quicker, to greatly cut emissions during warm up...
/daytripper '00 s4 6spd
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dave AKA vwdoc1 wrote:

Is probably the correct answer. IIRC the A6 and Passat are similar.
http://www.weirdlittlebiscuit.com/passat/leak /
Check the passenger footwell, as the CCU is there on Passats.
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Dougga wrote:

Your mechanic's estimate seems to be reasonable, the ABS module being the most expensive of the group. A regular problem, I could build a small hill with all the ABS modules I've had to replace over the years.
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