aadler

Hello,
I'm looking for a few tips on getting rid of a recurring fault code that keeps popping up on my 2000 S4(2.7 Biturbo engine). I keep getting a DTC of 17547 ( in both chipped and stock modes) which corresponds to a " Long Term Fuel Trim Add.Fuel,Bank2 System too Rich" condition. I've taken a look at the Bank2 add Trim value(block 32, value 3) and it is hovering around a 7. According to VAG-COM a +/- 10% deviation is allowable in that value yet my engine light comes on anyway. The strange thing is that both the Bank 2 and Bank 1 mult trim values (values 2 and 4) are hovering around 14 or so, well outside the 10% range but no codes are being generated.

As far as fixing it I gather the MAF seems to be the leading candidate based on the data in the measuring block- anything else I should check before I swap it out?

Thanks
Al

VAG com 303.1 w/ updated codes file

Uwe@Ross-Tech.com

that's at idle (or extremely light load). This is further confirmed by the fact that you idle trims in fields 2 and 4 are out of spec.

Look for vacuum leaks, or leaks in the exhaust before the first 02 sensor.

-Uwe-

aadler

According to the vag-com header 2 and 4 are the part throttle trims and 1 and 3 are the idle trims - are the labels backwards? Thats why I'm confused - the values that are out of spec are the part throttle, mult values while the idle trim values seem to be in spec, yet the DTC is the add version.

Uwe@Ross-Tech.com

when I'm tired and my brain isn't working well.

You're right 2 and 4 are "Part Throttle" 1 and 3 are idle. So the fact that 2 and 4 are off more than 1 and 3 does not jibe with the fault code being "Add".

Clearing the codes will reset all four trims. I'd do so, then drive for a while and see what happens with them.

To do a check on your MAF, log Group 002 for a full throttle run through 2nd gear. At full power (5000-6000) rpm, you should see a value in g/s that's roughly 80% of the HP your car is making -- say ~200 g/s on a stock S4.

-Uwe-

-Uwe-

aadler

Ok, I've cleared the codes and watched the group 32 trim values return to near the previous values after driving 15-20 miles, -6.6,14.8,-7.5,14.8. Interesting enough the fault code for the additive trim triggered for both sides this time 17547 and 17545. It seems to trigger once the values exceed about -6.5 or so. The bentley manual says the spec on the APB engine for all the values is +/- 4% so I'm definitely out of spec on all 4.

As for the MAF g/s reading from group 2 the highest I was able to get was about 151 g/s, that was at about 6300 rpm and 1.45 bar/boost; I have a tiptronic with a busted tip switch so I'm not sure what gear I was in. My guess would be 2nd from the speed and the rpm drop pattern when I stopped accelerating right after that shift. The power output was only about 85% so I'm not sure if I got all I could get - I was coming up fast on traffic at that point.

If this is a MAF I guess I can take it to the dealer since they extended the warrenty on the MAF component to 7yr/70k just last week; if its not I'm looking to DIY since the rest of the car is out of warranty. Any thoughts on if the MAF is the most likely suspect? I'm concerned that there may be a second problem that the dealer will find instead of the MAF(if thats the problem to begin with).

aadler

After I did the driving test I decided to do the basic electrical tests listed in the bentley manual, check ground, bat volts, etc at the maf plug. I also changed the air filter since it was quite dirty, and took a quick look at the maf screen to make sure there wasn't any debris. Everything seemed nominal. I put everything back together and cleared out the codes and started driving. Now I get this horrible shuddering off the line when I hit the gas. I checked codes and saw a 16487, MAF sensor signal too high, intermittent. After that I checked the logs from group 002- the MAF reading was going off the scale when I would start accelerating - over 350 g/s at one point which would seem to wack out the ECU and start the shuddering. Things then settle down until the next time I start accelerating. Now I get to see if the dealer will actually replace it under warrantly. Loads of fun