Frequently Asked Questions (FAQ), Procedures and Resources

[UrS4boy]

This is modelled loosely on the Audi 100/A6 (C4 92-97) FAQ Digest page (see URL)

This is how it works: Basically we put a short articles or links to good posts as replies to this thread. You can upload pictures to the audiworld.com and attach them to your articles. Please follow the structure of the thread.

Also if you are about to type a comprehensive answer, type it in the FAQ thread list below this post or make a link to it in the FAQ thread. Always check to see if a thread has already been started in the FAQ, e.g. Cam Position Sensor (CPS), etc.

TWO RULES:
- Please refrain from asking questions, flaming people or posting a thank you in this collection. Post those on the main forum!

- Try to keep links linking to other sites to a minimum since they may not be there in the future. The same goes for using pictures from someone elses picture poster; those will be gone at some time as well.

To find things, either browse down the list or if you want something more directed, use your brower's "FIND IN PAGE" feature.

Thanks from the staff at STFA (Search the Forum Archives)(or, on a bad day, Search the Freakin' Archives!!!)

• Link to C4 A6/100 forum FAQ - which has lots of common C4 BTDTs

[UrS4boy]

[UrS4boy]

The diagostics section is especially good. Scott also has parts for sale.

• http://www.sjmautotechnik.com/index.html

[UrS4boy]

Lots of stuff here. Especially transmission info. Charlie is the expert on that.

http://elektro.cmhnet.org/~audi

[UrS4boy]

The power output stages (POS) (2 of them) are located on a bracket on the firewall:

The POSs are electronic switches that eventually break down and fail. This typically happens intermittently until they finally fail totally, often just one channel at a time (total missing results).

The N122 and N127 are just names. They are identical. Both have 4 pin inputs (for 3 ECU inputs and 1 ground) and 3 pin outputs (for up to 3 coils). What is important that for the POS with the four wires coming into it from the ECU, you have the 3 wire lead to the coils connected to it (3 = 1,2,3). Likewise, the POS with the 3 wires coming to it from the ECU needs to be connected to the 2 wire lead to the coils (2 = 4,5).

The part number is 4A0 905 351A. However the brown Hitachi "351" (no "A") ones from the wasted spark V6s also work. I have no idea if they last long enough or not.

Link to a Bosch POS spec sheet

Here is more info about how the POSs work and how you might be able to steal the spare channel:

More POS info with X-ray photo link here

Here is a photo of the location of the two POSs:


See the other posts below for more info.

[UrS4boy]

[list][*]http://www.fap99.com/epcvsoapimc.epc...subcatid=80107

[UrS4boy]

Its a bit long but the detail is there to help us understand why they fail and how to "steal" the empty channel.

• http://forums.audiworld.com/s4s6/msgs/83085.phtml

[UrS4boy]

Besides being a long running joke at noobie's expense, it is under the rear seat. (Right hand side). Unless the battery is sealed, it should have a vent hose nipple. The car came with a clear plastic vent hose and it should be connected to that vent.

[UrS4boy]

People have tried other plugs but the Bosch F5DPOR still seem to run the best and last the longest.

The plugs like to "walk" their way out (with disasterous results) so checking them every oil change (3000 miles) is wise. Retorque to 22 lb ft turning ONLY clockwise (tightening). DO NOT backoff and then retorque. A simple beam-type torque wrench will do. You do not need a mega-buck digital torque wrench (unless of course you want an excuse to get one).

Link to the plug R&R below.

• AAN F5DPOR Spark plug R&R procedure.

[UrS4boy]

Our DOT headlights, in theory, cannot be fixed if you break a lense. However, the Euro cars had replaceable lenses SO...if you can score Euro headlight lenses from say, PG Performance or PUMA lighting, then you can replace them. Even if you don't need to change the lenses, you can still get in there and clean them. See the links in the posts below.