2006 audi a3 p0606 p0688 p2146 p2149 no start

[josh.13baker]

I've been trying to chase this issue for about 4 months now. it started out as intermediate not starting and i would get the codes p2146 and p2149 (fuel injector group A supply voltage circuit/ open) (fuel injector group B supply voltage circuit/ open) but id be able to get it to start by disconnecting the battery. Eventually it got to the point where the epc light came on, i lost all power and the car died and did not start again. I then went on to replace the fuel injectors and fuel pump relay, still wouldn't start. At this time I was also getting codes for improper voltage to ecu and sometimes no communication to ecu, this turned out to be because the battery was completely fried and once i replaced the battery the codes went away. Then decided to try and do the fuel pressure regulator, the car started and ran but i was then getting codes for fuel pressure regulator performance 2 and low fuel pressure at the rail. I then went on to replacing the high pressure fuel pump, this seemed to fix mostly all the issues the car was having as it drove amazing and pulled very strong with no fuel cuts or anything. I drove it an hour home from my buddies shop and the car died as soon as i got home, epc light came on lost all power and it died. I scanned the codes and I was getting a p0688 (ECM/PCM power relay sense circuit/ open) as well as p2293 (fuel pressure regulator valve (N276) mechanical malfunction) the N276 sensor arrived cracked when i bought it but i was able to super glue it in place (not a permanent fix) so i figured thats why i was getting that code. I decided to replace the fuel pump relay (also the ecu power supply relay) and the car started right up and ran great. I went to take it for a test drive and it ran great with no check engine light for about 15 minutes and then it started to run like !Removed! and then epc lost power and car died. i scanned it and I was then getting the same code again the P0688 but also im getting P0606 (ECM/PCM processor). i suspect my ecu has gone bad or i have some type of wiring issue, or short in the wiring thats causing the ecu power supply relay to go bad. im honestly stumped and do not know what to do with this car anymore, im about ready to give up. Side note: I have a used ecu off another a3 8p but i can not use it as it still has the immobilizer in it and I do not have the proper scan tool to rewrite the immobilizer code. I would like to know what chip inside the ecu is the immobilizer, I looked everywhere and I couldnt find anything on this specific ecu. 

[cliffcoggin]

Defective batteries are a well known cause for these sort of problems. Was your replacement battery new or secondhand? If the latter get a new one, then report back.

[josh.13baker]

Battery did not fix the issue

[cliffcoggin]

4 hours ago, josh.13baker said:

Battery did not fix the issue

That does not answer my question which I shall repeat: was it new or secondhand?

[Steve Q]

I'd definitely change the sensor that's been superglued. Also I'd recommend getting an auto electrican to take a look as you've replaced a good portion of the faulty components. If it is the ecu you'll need to get it coded to the car. 

[josh.13baker]

1 hour ago, cliffcoggin said:

That does not answer my question which I shall repeat: was it new or secondhand?

The battery was new and I replaced it with another new battery. 

[josh.13baker]

50 minutes ago, Steve Q said:

I'd definitely change the sensor that's been superglued. Also I'd recommend getting an auto electrican to take a look as you've replaced a good portion of the faulty components. If it is the ecu you'll need to get it coded to the car. 

I am changing that sensor today and also I’ve gotten a vag cable that is able to turn off immobilizer so I will be able to use my used ecu in the car to see if that fixes my issue 

[Steve Q]

16 minutes ago, josh.13baker said:

I am changing that sensor today and also I’ve gotten a vag cable that is able to turn off immobilizer so I will be able to use my used ecu in the car to see if that fixes my issue 

That's good then 🙂 please keep us posted on how you get on 🙂

[josh.13baker]

13 hours ago, Steve Q said:

That's good then 🙂 please keep us posted on how you get on 🙂

Changed the sensor on fuel pump and swapped the ecus and still nothing same issues. 

[Steve Q]

4 hours ago, josh.13baker said:

Changed the sensor on fuel pump and swapped the ecus and still nothing same issues. 

I'd be getting it to an auto electrican. 

[Dom05]

 

Edited April 18, 2023 by Dom05

[Dom05]

On 5/25/2022 at 6:01 PM, josh.13baker said:

Changed the sensor on fuel pump and swapped the ecus and still nothing same issues. 

Did you figure out what the problem is?

[Gbuck]

Check crank sensor wires you have a break in most likely ground or signal wire , I had to splice back all my wires to find the break in the wire 

Edited October 17, 2024 by Gbuck

[Schoess]

Hey guys, wanted to share my solution here. My 06 2.0t A3 had an issue where it would crank and crank and crank but no start. Eventually I got it to stumble start and it was then running down on at least 1 cylinder. After giving it some gas it would finally clean up and then run fine. I did not immediately have a CEL, but when checking with an OBD2 reader I got these 5 codes,

P0688 - ECM/PCM Power Relay Sense Circuit/Open

P2149 - Fuel Injector Group B Supply Voltage Circuit/Open

P0300 - Random/Multiple Cylinder Misfire Detected

P0303 - Cylinder 3 Misfire Detected

P0302 - Cylinder 2 Misfire Detected

After some research here and online, no clear answers were given. I saw a lot of people replacing a lot of parts and spending money by blindly throwing parts at the car.  When reading over the codes, I felt like most of them were "symptom" codes. The misfires are probably related to injector issues and the injectors not getting power is probably related to the PCM code. So I decided to replace my PCM relay, which in my car was not listed online or in the manual hardly anywhere. Here is a photo of the fusebox. The PCM relay is slot R1, circled in red.

 

After replacing the PCM relay, my car is running properly without issue. Hope this helps someone :)