Help with fault code 12555

[Pandito bandito]

Hello all long time reader but somewhat new to actually using the forum am looking for help with the 12555 I know I've seen plenty of threads on it but I haven't seen anyone really get a final solution. Anyways here's my problem

Ongoing check engine light comes and goes over the past year

12555- low pressure regulator fuel pressure outside spec. 008 implausible signal
12555-low pressure regulator fuel pressure outside spec. 004 no signal/communication

I have been to the dealer numerous times for diagnostic and have replaced the following already without success
High pressure fuel pump with follower
Low pressure fuel pump (tank pump)
Fuel filter
G410 sensor
Dealership seems to be at a loss for what's causing the fault and the car really isn't experiencing any noticeable symptoms runs starts fine still pulls great when you want to get up and go. Only symptom is the check engine light comes on when you start it half the time and when it's on its like it kicks the car into a limp/safety mode. Any help, info or insight on this matter would be greatly appreciated.

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[miA4]

http://forums.ross-tech.com/showthre...r-Audi-A4-2-0T

[Pandito bandito]

Thanks for the info. I have already replaced the low pressure pump ( Audi original parts with filter) had it done at the dealership so that shouldn't be the issue but I will be testing it when I get off work to confirm the numbers are reading correct just to double check that off my list.

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[miA4]

Thanks for the info. I have already replaced the low pressure pump ( Audi original parts with filter) had it done at the dealership so that shouldn't be the issue but I will be testing it when I get off work to confirm the numbers are reading correct just to double check that off my list.

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You definitely want to check the duty cycle of that fuel pump. If it's not working correctly, you may be able to have it warrantied if it is fact the fuel pump.

[Pandito bandito]

You definitely want to check the duty cycle of that fuel pump. If it's not working correctly, you may be able to have it warrantied if it is fact the fuel pump.

Yeah I'll check it this afternoon when I get off if it's bad it should be covered pump was installed less than a year ago (this spring I think have to check my records)

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[p0isin]

Data log of low pressure fuel system pressure and the lpfp control module would help you figure out the issue. Without that, maybe it's the lpfp control module (unlikely) or sediment in the fuel tank which can partially clog the pump during use.

[Pandito bandito]

Data log of low pressure fuel system pressure and the lpfp control module would help you figure out the issue. Without that, maybe it's the lpfp control module (unlikely) or sediment in the fuel tank which can partially clog the pump during use.

OK follow up question how to DATA log. I have a schwaben scan tool with vagcom but have only used it to pull codes. First time using a scan tool kinda learning as I go.

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[Pandito bandito]

OK guys just got home an had time to put him on the scan tool here's what I got

Ignition ON
engine ON

at idle

103-1 current pressure 5.19 bar
103-3 adaptation value 2786
103-4 ADP OK

106-1 fuel rail press 49.92 bar
106-2 electric pump 83.1%

140-1 49.92 bar rises with throttle saw 110 bar before I left off

230-1spec. fuel press. High 49.92 bar
230-2 act. Fuel press. High 49.28-49.92
230-3 max deviation. 50

Please let me know if this makes sense to any of you or if any of you notice anything wrong with those numbers from what I've read the only thing that looks off to me is the measurement for 106-2 I've read should be around 50% tops?

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[Pandito bandito]

You definitely want to check the duty cycle of that fuel pump. If it's not working correctly, you may be able to have it warrantied if it is fact the fuel pump.

Check the values just now posted further down the thread if you have a chance lemme know what that looks like to you. Much appreciated

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[Charles.waite]

I bet the Fuel Pump controller is hosed. The pumps are very stout they're the same pump as in the RS4, the pump controller is a joke though and prone to failure. It handles some high currents so when it starts to go it often throws acode saying the pump is failing to meet required flow, when in actuality the pump is fine, but the controller is failing to push enough current to drive the pump properly. If we're doing parts darts, I would put my money on the controller.

And before people bring up the RS4 controller, yes its more stout, but I believe it needs to be tuned for specifically. I don't think its a plug and play solution.

[Pandito bandito]

I bet the Fuel Pump controller is hosed. The pumps are very stout they're the same pump as in the RS4, the pump controller is a joke though and prone to failure. It handles some high currents so when it starts to go it often throws acode saying the pump is failing to meet required flow, when in actuality the pump is fine, but the controller is failing to push enough current to drive the pump properly. If we're doing parts darts, I would put my money on the controller.

And before people bring up the RS4 controller, yes its more stout, but I believe it needs to be tuned for specifically. I don't think its a plug and play solution.

See that is what I was leaning towards as of today. The low pressure pump was replaced within the last year with original parts from dealership so I didn't think it could be the pump itself unless they installed a faulty one. And the rest of fuel system is pretty new as well HPFP, fuel filter and G410 sensor. Also after scanning values all the numbers look correct with exception of the pump load an being that the pressures still look correct it leads me to think that the pump load percentage I'm reading is erroneous.

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[Pandito bandito]

So talked with my local dealers service rep an based off the data I pulled he seems to agree that it sounds like the fuel pump module. Now I just gotta find time to take it in an have them check it for themselves. Thing that bothers me most is why they didn't check the module before they had me dish out for a new low and high pressure fuel pump and sensors. Seems like I could've avoided a lot of experience with just a Lil extra diagnostic up front. If it is the module hopefully I can talk them into covering it as a goodwill repair.

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[Charles.waite]

Good luck. The part cost and labor for those isn't much at all I don't think so hopefully they cut you a break on it and maybe just ask you to cover the cost of the part.

[Shanster]

Relplaced my LPFP recently too and I had crazy issues with the car not turning over. Apparently there is a TSB that says if you replace the LPFP with a newer revision, you need to replace the control module too. From what I understand, Audi knew the old pumps were not giving adequate fuel, so the newer pumps pull more current and the old control module can't handle it. The car doesn't go into limp mode, it just shuts off.

The location of the LPFP control module is a nightmare. It's located between the fuel tank and the underside of the cabin (cockpit?). You have to drop the fuel tank a little bit and press up on the sheet metal of the cabin to install it. It's a prick of misery.

[Pandito bandito]

Relplaced my LPFP recently too and I had crazy issues with the car not turning over. Apparently there is a TSB that says if you replace the LPFP with a newer revision, you need to replace the control module too. From what I understand, Audi knew the old pumps were not giving adequate fuel, so the newer pumps pull more current and the old control module can't handle it. The car doesn't go into limp mode, it just shuts off.

The location of the LPFP control module is a nightmare. It's located between the fuel tank and the underside of the cabin (cockpit?). You have to drop the fuel tank a little bit and press up on the sheet metal of the cabin to install it. It's a prick of misery.

Yeah that's what I was reading when I was looking into doing it myself. I've had it in the shop multiple times for this issue so I'm hoping I can get them to just pony up for the module repair beings they already got me for a high pressure and low pressure pump plus sensors. I've taken my car to the dealership exclusively since I've had it so I'm hoping something can be said of my loyalty.

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[Shanster]

So when you got your code that said your LPFP was shot, they didn't also replace the controls module for it? This was a technical service bulletin so the dealership should have known this. That sucks that they made you replace other things before realizing it was just the CM that also needed replacing.

[Pandito bandito]

So when you got your code that said your LPFP was shot, they didn't also replace the controls module for it? This was a technical service bulletin so the dealership should have known this. That sucks that they made you replace other things before realizing it was just the CM that also needed replacing.

Yeah that's my beef with it. If they'd have done a Lil more upfront diagnostic or looked through their service bulletins they'd have caught it before replacing both pumps. Out of curiosity would you happen to know the TSB that pertains to the control module? Would be handy to have in hand when I go to the dealership.

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[Pandito bandito]

So to update going back to the dealership Friday to have them check fuel pump control module. Reached out to Audi North America an they have assigned me an regional representative to oversee the diagnosis and reach a solution with this issue. We'll see what happens Friday but I do have to say I'm pleasantly surprised with the amount of help I've received so far from Audi North America considering the car is ten years old. Everyone I've talked to seemed to genuinely want to help resolve the issue an get my car back to peak performance. Fingers crossed.

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[Pandito bandito]

Update. Took the car into Audi yesterday to have them check on the fuel pump control module an troubleshoot the rest of the fuel system. Tech said everything in the car checked out an they still couldn't figure out why the code was popping up. Regional tech chimed in that they should check the fuel lines. Blew air through the fuel lines an got a bunch of cruddy black sludge out of the lines. They cleared the fuel lines out test drove it an hooked it back up to the computer and the duty cycle on the pump is back to normal numbers as of now haven't had the code pop back on hopefully that was finally the fix. Just kinda aggravated that we didn't check the fuel lines sooner. Anyways hopefully that was the issue and for anyone else experiencing the 12555 code have them check your fuel lines before replacing parts only cost a couple hours so it's far cheaper than replacing any parts first.

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[Okedokey]

Update. Took the car into Audi yesterday to have them check on the fuel pump control module an troubleshoot the rest of the fuel system. Tech said everything in the car checked out an they still couldn't figure out why the code was popping up. Regional tech chimed in that they should check the fuel lines. Blew air through the fuel lines an got a bunch of cruddy black sludge out of the lines. They cleared the fuel lines out test drove it an hooked it back up to the computer and the duty cycle on the pump is back to normal numbers as of now haven't had the code pop back on hopefully that was finally the fix. Just kinda aggravated that we didn't check the fuel lines sooner. Anyways hopefully that was the issue and for anyone else experiencing the 12555 code have them check your fuel lines before replacing parts only cost a couple hours so it's far cheaper than replacing any parts first.

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Interesting. May be add some techtron or similar to the tank to make sure you clean it all up. BTW, if you need a module, I have one you can have for postage only.

[Charles.waite]

If they haven't replaced the fuel filter through all this I would do that too. Crap in the lines is exactly what the filter is supposed to prevent.

[Pandito bandito]

Yeah I was thinking about running a cleaner through the tank. I do appreciate the offer on the module but as of now all seems to be running fine and I'd hate to grab it from you, not use it an then someone else actually need it.

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[Pandito bandito]

If they haven't replaced the fuel filter through all this I would do that too. Crap in the lines is exactly what the filter is supposed to prevent.

Filter was replaced by Audi earlier this year when the did the low press pump how they didn't notice all the sludge when they did that I do not know.

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[Pandito bandito]

Well was good for a couple week but check engine light just came back on this evening. Have to code it when I get home but at this point I expect it to still be the 12555 code. Ugh

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[Pandito bandito]

OK update. After blowing out fuel lines went a good couple weeks without code then it came back. Started going through receipts and log books noticed codes started about the same time I moved and had to switch gas stations. Station I was using was brand new and a top tier company. Station I switched to was the same company but it was an old station with underground tanks. Have run a fuel treatment through the car and switched stations. Knock on wood haven't had the check engine light on in a month now. Pretty sure the station I was going to had crappy dirty old tanks full of sediment.

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