Audi A6 C6: Performance Diagnostic Guide

This article applies to the Audi A6 C6 (2004-2011).

The Audi A6 is a relatively reliable automobile; however, just like any vehicle, there are always opportunities for problems. Cars are made up of moving parts that create friction, which causes wear and some of this wear is in places that are not seen without tearing things apart. One doesn't just tear things apart during routing maintenance. Tearing things apart is costly and time consuming and isn't normally done until a problem presents itself. There are some very common issues with the A6 C6 model that range from the simple and cheap to the very complex and so costly that you'll immediately consider selling. Learn what issue your symptoms might indicate and whether or not you can take them on yourself or have to relegate to the pros. The best defense is knowledge, so read on and learn what your car may be telling you so you can make an informed, smart decision.

Step 1 – Find the reset button

One very common issue is an A6 that cannot shift out of park.

Addressing this one up front seems handy, as a lot of people assume there is an engine issue when this occurs. If your A6 is locking you in park and preventing you from going into drive, your engine either has had a serious malfunction and gone into limp mode (with the check engine light illuminated), or you have another, unrelated and somewhat common issue, which is actually with the transmission.

If you need to immediately get going, you will find a small cover under the ashtray. Use a flat head screwdriver in the slot to pop the cover off. Inside, you will find a white button in a stainless steel grommet. Press in this button and your car will now shift back out of park. This is only a temporary solution, as it will happen again.

• This issue indicates a bad gearbox CU, otherwise known as a transmission control module.
• The TCU was engineered inside of the transmission, which exposes it to very high temperatures.
• The TCU fails and needs to be replaced or reprogrammed, and is very costly.
• The dealership will charge upwards of $1,500 to do this; DIY can be much less costly, and doesn't require a lot of mechanical aptitude.

If your car is not only locked in park, but won't start while everything else works just fine, you have a bad steering column.

Step 2 – Check out your steering column transponder

A very common problem with these cars is the steering column transponder going bad, which is what recognizes your key to start the vehicle.

Unfortunately, when your car won't start, but the dash lights up as well as just about everything else, you then know that your battery is good. You may have a bad alternator, which is not likely your only problem. The bad alternator may be the catalyst, which fried the steering column transponder. You can save yourself a little money by changing the alternator yourself, but unfortunately you must go to Audi to have the transponder reset, or, in many cases, the entire steering column replaced. This is going to run several thousand dollars. Be sure to research this problem with Audi resources to see if you are able to find any kind of relief for this if your car is no longer under warranty.

If your steering isn't locking, but you are experiencing rough starts and idles, read on for some insight.

Step 3 – Check out your OBD codes

A common code thrown is P0346: Camshaft Position Sensor.

The camshaft position sensor can cause a myriad of symptoms, but those same symptoms may not exactly be a camshaft position sensor. There are a few different things that can be the culprit, and you might be in luck as to the cost of the repair.

• There are four camshaft position solenoid valves. If any one of them goes bad, you could get the P0346 code.
• A single valve can be had for around $70 and it will take you about 10 minutes to replace if you have no skills whatsoever.
• There are also two cam tensioner sensors that are adjacent to the spark plug coils. They are screwed in with a single Allen wrench type screw and connected up to a wiring harness quick connect clip.
• Pull these two sensors and clean them up to see if your code goes away. Otherwise, you can try replacing them to see if that works.

If you have a different MIL code relating to the camshaft position sensor, make sure you are sitting down and read on.

Step 4 – Look into passenger side upper chain tensioner

The upper chain tensioner goes bad and causes the timing chain to "stretch," which can throw the P039 code.

A very common and very costly problem with the A6 C6 is the upper timing chain tensioner on the passenger side. For some reason, this tensioner can go bad, or rather, will go bad at some point. When that happens, it causes slack, otherwise known as a "stretched" chain, and causes very poor engine timing, which is bad in the your-engine-is-going-to-break kind of way. You will hear the pistons knocking so bad that it sounds like your car is a diesel. The sound may go away once warmed up or moving. Don't let this fool you into thinking that the problem went away. If this is the case for your Audi, we strongly suggest shutting the car off immediately and having it towed to a repair shop. The Audi professionals will possibly charge many thousands of dollars to drop the engine as well as the transmission to tear it apart to change the timing chain and the tensioner. If you search around for a very good indy shop who knows these cars well, they can likely change the tensioner out without dropping the engine and transmission. This will save you a ton, but you will still be looking at a bill of well over a couple thousand, as replacing timing chain components does require a complete tear down of the front of the engine and all related timing items.

If your problem isn't a rough ride, but one that dies for no reason and no warning, you might have a fuel problem.

Step 5 – Check fuel filter and pump or crank shaft position sensor

Either one of these can cause your engine to just stop without a sputter or stall, but a complete shutdown which is remedied after a few minutes of cool down.

So you are cruising right along and suddenly, and without warning, your engine shuts off. Everything else seems completely normal. This is a normal result when a few different things go bad.

• Start with the crankshaft position sensor. This is a relatively inexpensive and easy fix that you can do on your own with little mechanical aptitude.
• Change it out and see if the problem returns.
• A second common issue with these cars that will lead to your problem is a bad fuel pump.
• Replacing the fuel pump isn't too difficult, but it is time consuming and pretty costly if you have a pro do it.
• If you have a pro do it, fork over some extra cash to have them change the fuel filter as well. Clogged fuel filters can cause the pump to overwork and die early. Changing the pump without the filter will leave you with a false sense of security, as the problem will appear fixed until the new pump eventually dies prematurely because the source of the problem is actually the filter.

Related Discussions

• 2006 A6 Won't Start, Cannot Even Get It Out of Park - AudiWorld
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• CEL: Camshaft Position Sensor (P039) - AudiWorld
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