carlzimmerman

F***! Just when I thought I would be able to enjoy my beautiful car in perfect condition - check engine light P2404 is back on. Back to Audi for more diagnosis.

A6Gary

If your Audi dealer ever figures out the solution for this problematic DTC, please let all of us know so we can fix our cars. Thanks!

carlzimmerman

I have had this issue since 2012 - I have now had two LDP pump replacements, blowoff valve replaced as a fix at some point, car smoked for leaks and continuously found nothing, new wiring, new gas cap, I think it has to be the ECM. I ordered a used ECM online with the exact number and had audi try to reprogram it to my car (2005.5 Audi A4 3.2l) - except it was a Stage 2 chip I had bought instead of a stage 1, and you have no way of knowing otherwise.

The good news: I was able to get the car inspected after driving it straight to the inspection station so I am good for another year. Also, the Audi of Charlotte has one of the top audi mechanic instructors, so I am going to request he take a look at it because two other audi dealerships and three independent shops cant seem to figure it out.

ILLusive

Has anyone tried updating their ECM firmware to the latest? I believe its 0050. I may as well be the guinea pig here and bite the bullet. milan_o did the ECM replacement and the code eventually came back. This is so frustrating!

chino26

I asked my service writer about this firmware update yesterday. I had already paid 1.5 hrs to diagnose, only to be told it would take more time. So that money is flushed, and the light came back on this morning (as they said it probably would). My paperwork says "likely ECU or LD pump, more diagnostics required". So, has anyone had better luck at the dealer?

So far, gas cap and purge valve replaced. Checking the vacuum line by dipstick this evening as well.

carlzimmerman

What Audi dealer are you with? I am with Audi of Charlotte. Maybe we can have them collectively file a case to Audi about this nonsense. I have had LPD replaced, gas cap, smoke tested etc. they tested the ECU and said it was fine, came back on a day later, so then they call me, say it's the same problem and for 2 hours of diag to check wiring and vacuum. They have not called me back and it is day 2 of me having this ****ty *** 2016 A3, my 2005.5 A4 3.2l is way classier. Since they have already told me the ECU was fine, it will be VERY interesting to see what they determine next. The good news is I was able to get it inspected immediately after replacing the pump and have another whole year to figure it out.

A6Gary

Since your Audi dealer has determined that the ECU is OK, and the wiring, LDP, N80 valve, vacuum lines, gas cap, etc., etc. are OK also, then it would appear that the ECU software is the problem. Based on your experience and others, there isn't other hardware/component to check, so it has to be a software issue.

carlzimmerman

I agree. The only thing I have not replaced is the charcoal gas canister, but the dealsership said that would show a separate CEL code. I am going to insist that they reinstall the firmware even though they said it is up to date. If they come back and say it is actually the ECU, I will require them to provide me with a diagnostic report from the ECU that shows the ECU is actually defective. I have had this code since 2012, and honestly, the only way I see this being resolved is if we all collectively have our dealships coordinate a case study to Audi North America on how to resolve this issue. I have also requested to keep the LDP pump and may try to find a way to submit to Audi to see if it was actually the wrong one. Maybe we could even collectively file a case to Audi North America to show them this isn't an isolated issue.

milan_o

Just for clarification, I replaced the ECU with a used one and the code came back. I did recently speak with the person that runs the shop at the local Audi dealership. He said he was familiar with the issue and I would need to replace the ECU to fix it.

I have not decided yet to buy a new ECU or just keep it as is.

carlzimmerman

Thank, Milan. It's day 5 now and they have the top Audi mechanic in North America (apparently he helps train other mechanics) on it. They are checking wiring etc and running more tests, but told me may be ECU after all. If it's the ECU, and if reinstalling software doesn't work, I will probably just keep paying extra to pass inpection every year since everything else is solid.