This car does not start. When I first checked, I found that battery was dead and there was a lot of water in the battery compartment due to drain block. I drained out the water and changed battery. Now when I try to start, it just clinks. When I scanned, I got the following codes:
PO600
P0276
P0445
P0261
P0267
P0270
P2401
P0418
P0273
P0414
P0264
P0057
P0037
P0230
P0141
P0161
P0321
When I checked these codes, most of them say circuit low (e.g., cylinder 1 injector circuit low, cylinder 2 injector circuit low...) O2 and HO2 circuit low.When I further checked for the causes, besides many possible causes for each, I found that ECU failure was on the list of causes for each of them. So, I'm now thinking that the problem is dead ECU. I'm new to Audi, can you guys give me suggestions as to how I can solve this problem. If I get a used ECU from the same model, do I need to reprogram it?

 

I'm thinking the battery doesn't have enough cold cranking amps to turn over the engine. Over time the battery will in a sense lose its ability to hold enough of a charge, although you may think it's fully charged.

The "clicking" that you noted is very common for this condition.

 

^+1
What he said.

 

Thank you guys. I did replace the old battery with a new one. When I did that, the car just cranks, but does not start. I opened ECU compartment and found that there still was some water. I've now made it dry, but suspect that water has damaged ECU and/or harness, or/and connector. Would appreciate all your help and suggestions.

 

Most circuit low faults (i.e. low voltage) stored in a vehicle's memory are just that, codes set when the battery voltage went too low. They mean nothing if after clearing them, none return. The modules only log low voltage faults as an aid to diagnosis if the need arises.

Remove the ECM connectors and examine them for corrosion (white or green colors). If found, chances are you will need a new ECM and replace the corroded terminals in the hardshell connectors. All the terminals with wire pigtails (about 12" long) are availbale from the dealer. Warning, the price will shock you and I'm not joking.
If you get a used ECM, yes it will need to be adapted to the car (programmed). This can be a problem with Audi's. The old VIN and vehicle specific coding has to be erased from the replacement ECM and the VIN and coding for YOUR car must be installed into it. It doesn't always work, especially if the old ECM is "dead" and you can't upload the info to the scanner to download into the new one. It is possible to do on-line coding but only a dealership can do that. The coding for your VIN is stored in the Audi database and is only accessible by a dealer tech with a GeKo I.D. (a security precaution). It may need to be done on-line anyways to deactivate component protection (also a security measure). Don't mean to scare you, just giving the worst case scenario. Actually, worst case would be a new ECM and they're about $1,200 if I remember correctly.

 

Yikes

 

For a 3.0 liter the ecu is 723.79 dollars for a reman unit, and it's 3 days away to order in. Plus a 160.00 dollar core charge. But we may have to send it to Audi to be inspected before we give core credit back to the owner. The ecu can not show signs of being opened up, terminals must be in good shape, not missing or damaged. Usually core money is refunded to the person that bought the ecu. The only time there is cause for concern is if the ecu was submerged in water. Then we have to wait for Audi to evaluate it and give us core credit first. Should the ecu be something that isn't rebuildable, then you wouldn't get the core charge of 160.00 back.

 

I actually inspected fuses and relay panel and found that fuel pump relay was missing. When I installed it, my car started and I could change gears and the car goes back and forth with gear change. But when I push gas pedal, it does not accelerate though engine rpm changes. I can see that hydraulic pump relay is still missing. Are there any fuses or relays that affect acceleration. Also, when the car starts, the ESP signal remains and check engine light is on.
One update. I found that two small hoses on the upper front side of the engine are leaking (one seems to be completely broken). Does that have anything to do with acceleration? I'd appreciate any help.
Thank you all.

 

I also found that ABS fuse is missing. And passenger side floor is wet. So, TCM can be damaged. Also, when I tried accelerating, I saw some smoke coming from the back part of the engine on the passenger side. The smoke was not white or blue (perhaps it was black.) Any ideas?

 

Please keep posting because I have the similar problem with my 2002 A6 Avant wagon. It's silent when trying to start but the amps read 12-14 even though the battery is 4 years old?