I have a 2003 A6 3.0 Quattro and lately it's been giving me hell by randomly dying on me. I'm suspecting there is a short somewhere, especially that plastic around the (+) terminal is a bit melted, and it's a 3mo old battery. I also suspect it may be the starter but wouldn't know where to start with that one. In any case, see below and hopefully someone had the same problem or knows what it is.

Conditions: Check Engine on, ABS on, EPC on, Brake symbol (screen, not panel - a big circle), Oil Sensor symbol (also screen). Not so long ago someone in a shop pointed out an ripped wire by the front driver-side wheel so I assume that's why ABS and Brake symbol are showing. I assume oil sensor simply went out and needs to be replaced.

Synopsis: The car was turning on fine, up until one day I drove to work and about 2.5 hours later it would not start. You could at first hear the starter, but after a few attempts it went dead. I figured the battery died because of a short or something but didn't have any instruments to confirm - it was simply dead, had to even close it with the key. In the evening, I got a jump from a coworker - it took a few turns of the key before it started - and brought it to PepBoys. They figured it was a 3-way DC splitter I had plugged into the cigarette lighter that drained the battery (never mind nothing was actually connected to any of the three outputs). That sounded wrong to me but they explained that "it slowly drained one terminal of the battery" and that's why it died now and not a week ago when I first plugged it in and started leaving it plugged. Still sounded wrong but the car started and it was fine for a couple of days, when I drove to take the garbage out to the dumpster, came back and 10min later it wouldn't start. At that time, I got it jumped again and it was fine for a couple of days. Then it died again. This time I jumped it again so that I can at least come home and today, I decided to get some readings off of it and see what's up. And here they are:

(I) BEFORE TRYING TO START THE CAR:

While clamps are connected to the battery:
1. V on battery terminals = 12.37V
2. Battery load @12V setting = 12.35V
3. Ω between battery terminals = 0.00 pulsating 0.L (∞) about each second
4. Ω between (+) terminal and frame = 0.00 pulsating 0.L (∞) about each second

While the ground (-) clamp is disconnected from the battery:
1. V on the batter terminals = 12.44V
2. Battery load @12V setting = 12.40V
3. Ω between battery terminals = 0.00 pulsating 0.L (∞) about each second
4. Ω between (+) terminal and frame = 0.L (∞)
5. Ω between (+) terminal and ground clamp = 0.L (∞)

(II) TURNED IGNITION - CAR STARTED - TURNED OFF CAR

(III) TOOK OBD-II READINGS:

A/T, SRS, ABS show no codes
Engine shows 10 DTC codes:
01. 16502 - Engine Coolant Temp.Circ High Input
02. 17887 - Brake boost vacuum system
03. 17544 - Long Term Fuel Trim Add.Fuel,Bank1 System too Lean
04. 17546 - Long Term Fuel Trim Add.Fuel,Bank2 System too Lean
05. 18011 - Internal Control Module Malfunction
06. 18010 - Power Supply (B+) Terminal 30 Low Voltage
07. 16684 - Random/Multiple Cylinder Misfire Detected
08. 16685 - Cyl.1 Misfire Detected
09. 16686 - Cyl.2 Misfire Detected
10. 16687 - Cyl.3 Misfire Detected

(IV) TURNED IGNITION - STARTER CLICKS ONCE - CAR DOES NOT START

(V) TOOK READINGS AGAIN:

While clamps are connected to the battery:
1. V on battery terminals = 12.37V
2. Battery load @12V setting = 12.31V
3. Ω between battery terminals = 0.00 stable
4. Ω between (+) terminal and frame = 0.00 stable

While the ground (-) clamp is disconnected from the battery:
1. V on the batter terminals = 12.39V
2. Battery load @12V setting = 12.35V
3. Ω between battery terminals = 0.00 pulsating 0.L (∞) about each second
4. Ω between (+) terminal and frame = 0.L (∞)
5. Ω between (+) terminal and ground clamp = 0.L (∞)

I am not much into electrical things so I'm a bit confused about the Ohm reading going between 0 and infinity at what looks like a measured pulse. But the difference I see is that it was pulsing before the car started and stable 0 when it couldn't.

Also, when I jumped it last time, after a few minutes the revs started going up and down while it was idling. I don't know if this is related or not.

A short? Or could be the starter not catching flywheel? Something else (I ruled out the neutral safety switch)?

 

You are overthinking the problem. I would suspect your cars Issues lie in your OBD 2 results rather than a short in your electrical system.

(III) TOOK OBD-II READINGS:

A/T, SRS, ABS show no codes
Engine shows 10 DTC codes:
01. 16502 - Engine Coolant Temp.Circ High Input
03. 17544 - Long Term Fuel Trim Add.Fuel,Bank1 System too Lean
04. 17546 - Long Term Fuel Trim Add.Fuel,Bank2 System too Lean
05. 18011 - Internal Control Module Malfunction
07. 16684 - Random/Multiple Cylinder Misfire Detected
08. 16685 - Cyl.1 Misfire Detected
09. 16686 - Cyl.2 Misfire Detected
10. 16687 - Cyl.3 Misfire Detected

Those are serious errors. Sounds like your car is running lean and overheating, it shutting off might be its way of trying to protect itself, you need to figure out why its running lean like this. Id start by diagnosing the fuel system.

1. Check if the car has any "performance" reporgramming, or that the ECU hasnt been medeled with.
2. Consult the service manual for the procedure to diagnose the ECU from its voltage output and input signals. Every car has this,
3. Check the spark plugs and post pictures of them.
4. Check the injectors, and fuel pressure. If your injectors arent firing properly or they are dirty that can cause a lean reaction.
5. A bad sensor can cause a car to think its running lean when its not. The service manual has instructions on how to check all your sensors and determine if they are operating properly. The tests are usually fairly simple some are more complex and require special equipment like an oscilioscope. The majority though are very basic
6. If youve tested everything and cant diagnose it there is no shame in going to a certified Audi tech nerearby for help. Its not so much a question of knowledge as it is a question of resources,

Last thing you want to do is spend a bunch of money replacing parts not to solve a problem. Do the service anual tests first.

HEre is another source of information:
Hints and Tips : Audi idle speed problems

 

Thanks for the reply! I took the car to a dealer and had it repaired - so far it runs much smoother and no dead time. They did mention that the new battery I have in it drains out and is faulty so I'll have to replace that. You are right - no short. I hope the list of what's wrong with the car below helps someone

* Major vapor leak, tubing and vacuum hoses worn out
* Coolant temperature sensor does not work (this is likely what prevented the car from starting - never would have thought of it)
* Oil sensor - well, I mentioned that, it just needed replacement
* Front wheel speed sensor - wiring needed replacement
* Rear break caliper piston - the break is pushing on the wheel so the wheel rotates slower than the other three
* ABS control module is faulty - that's what causes the ABS/EPC light to go off

There are still a couple of things I'll be taking care of (small oil and transmission fluid leaks) but that's about it. Not going to PepBoys anymore - they have no clue.

 

Hi I bought an Audi A4 Quattro turbo 1.8 of the year2003 a year ago. When I bought it there were a couple of indications on the cadran but my car was functioning without any problems. I know that its computer had some issues but I was able to use the car without problems. I could turn it on without any problems and one day in the morning I tried starting my car and it wouldn’t start. The battery was dead. We jump started it but my alarm system was going crazy for a while. I turned the engine off and the alarm stopped. When I turned it back on it the engine started. However the following morning the car wouldn’t start again. We brought it to the mechanic and he told us that the battery of the remote locking system needed to be chanced and he changed it. The car worked without the alarm setting off and the following day the car was working properly. Unfortunately though the next day and ever since, the car wouldn’t start and it seems that the battery is drained. Is it possible that the problem is from the central computer? Or could it be something else?