[Biturbos4] Help with a few fault codes

Michael Benno mbenno at yahoo.com
Fri Mar 4 14:45:15 EST 2005


IIRC from my 2001 S4Avant, you are correct the you should have the revised TBB and possibly the clamps. However, you definitively want to check, especially the clamps. When I went to replace the TBB on my 2000 A6 2.7t the dealer only gave me the TBB and said the clamps were not needed (I called BS and ordered the clamps). 

Here are the part numbers: 
-Boot new part # 078-133-356T 
-New main clamp# 078-133-343 

Here is the AW link on how to repair it: <http://www.audiworld.com/tech/eng19.shtml>

Also, I here is another link to some of my boost test data, this one is a little easier to read: <http://pictureposter.audiworld.com/14326/mtm-boost.jpg> Please note my test data was with the MTM stage 1 chip done in second gear.

Your dealer can easily spot boost leaks by looking at he fuel trim levels. Fuel Trim is the fuel that is add/subtracted to the forecasted mixture based on the O2 sensor readings. A boost leak will create a gap (you can search for fuel trim explanations on the AW forums. There is a detailed explanation in there somewhere). Ask your tech to look at the fuel trim levels (there are two fuel trim measurements) have them tell you if they are in/out of spec. 
Mike Benno
2000 A6 6spd MTM1

Quincy Chiang <b5quattro at shaw.ca> wrote:
Hi Mike and all,
> First are you chipped? 

My car was chipped for 2 weeks last fall, but not at the moment. The thought of blowing the K03s when I don't have the cash to replace/upgrade is just too much to bear! ;-)

> The engine code is infact a boost leak, I would check/test the 
> usual suspects, 1.TBB, 2. BBV, 3. F-hose, after that you can do a 
> pressure test to see if there is leaks somewhere else (ego IC end 
> caps, turbo cold side connections.  

The BPV's are brand new 710N's from last summer, so I think they should still be ok. I think I'll definitely check the TBB first.

> Regarding the TBB, if you are not running the later or an upgraded 
> version you may want to just as a matter of course. A stock 
> replacement is less than $15. Make sure you get the revised clamps 
> as well (I can give you the PN if needed). Look for cracks on the 
> old one where the clamps go. 

P/N's on the new boot and clamps would be great! Although don't the '01.5 cars come with revised TBB and clamps already?

> Regarding the BBV you need to test with vacuum pump, they should 
> hold vacuum for at least a couple of minutes. 
> I can give you a hand if needed. 
> Regarding your logging tests you should be using 3rd gear rather 
> than 2nd gear for acceleration tests. 3rd gear gives you much 
> longer sample times. The sampling rate fo VAG-com is a little 
> slower so you will see greater deviations with smaller windows. 
> You can take a look at my boost tests (also done in 2nd gear) <" 
> target="l">http://pictureposter.audiworld.com/14326/115-each-
> test.jpg> 
> I had the same questions about lags between specified and actual 
> boost. In 3rd gear these deviations are must less.

In that case the 3rd gear pull seems to produce similar results as yours. It's too bad the laptop that's running the VAG-COM software (also borrowed) is so old, it doesn't even have a floppy disc drive to transfer the data!

Now my car is still under warranty, I think I'll drop by my dealer early next week and see what they can find out. I know I can probably check for boost leak myself, but there's no sense of me paying for a new TBB (seems to be the most likely culprit) when it should be free under warranty.

Thanks Mike for your help!


> Quincy Chiang wrote:
> Hi everyone,
> My car's been feeling slightly down on power lately, and the boost 
> doesn't seem to be holding at 9 psi anymore (from boost gauge), 
> more like 7-8 psi only. So I was doing some data logging last 
> night with a borrowed VAG-COM, but the results were somewhat 
> inclusive.
> When I stomp on the gas in 1st of 2nd gear, the requested boost 
> would shoot up and the acutal boost would lag by quite a bit and 
> doesn't get to the requested level. But in 3rd gear, actual and 
> requested boost seems to be on par. Didn't do any logging in 4th 
> or higher gears as I didn't need a speeding ticket. I'll play 
> around with it some more.
> But here comes my question... while scanning for fault codes, I 
> got the following two codes:
> Engine
> 17965 - Charge Pressure Control: Positive Deviation
> P1557 - 35 - 10 --- Intermittent
> Radio
> 65535 - Internal Control Module Memory Error
> 00 - 00
> Does anyone know what these are? I suspect the first one has 
> something to do with my wierd boost behaviour. Thanks in advance 
> for your help!!
> Quincy
> '01.5 S4
> '90 CoupeQ
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