# P3045 fuel pump stays on



## Lilblonde1993 (May 14, 2016)

Hi guys new user here.

I have a 08 TTR

I'm currently away with family and my battery went flat, I called the AA and he done some investigating and we could hear a Hoover like noise coming from the fuel pump even with the ignition off.
He ran a diagnostic check and error P3045 was present 
"Fuel pump control unit defective"

I've not had any problems with it stalling.

The Aa man has disconnected the neutral on the battery for now until I decide what to do?

I have phoned up some main dealers and sourced the oem replacement part, but it will take four days to get here.

Plus Audi want a small fortune to diagnose and for labour charge.

My dad is here who is fairly handy with tools, I have tried looking on the net to see how accessible the part is but not had much joy.

Any advice would be greatly appreciated.

Thanks Emily


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## Lilblonde1993 (May 14, 2016)

Any advice on testing the module or gaining access?

Thanks


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## brittan (May 18, 2007)

On a TTR with 2.0 litre engine the control unit lives under the trim panel behind the RH seat.

See: http://manuals.co/workshop/audi/tt/tt38/4022/29
The control unit is the L shaped item next to the black arrow and its cable goes through the rubber cover and plugs into the top of the fuel pump.

Control unit looks like this: https://deutscheautoparts.com/2-0-t-fue ... 6093g.html

Also note that the fuel pump is energised when the car is unlocked or the door opened. Check for correct operation of the interior courtesy light to confirm correct operation of the door lock switch.


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## Lilblonde1993 (May 14, 2016)

Thanks for your reply,

Would the door or interior light issue throw up the fault code P3045

Thanks
Emily


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## brittan (May 18, 2007)

I'd have to trawl through the book to be certain but I'd expect the 'stop' signal to the fuel pump to come from the ignition switch rather than the door. Hence I'd go with the control unit.

Bad timing with the weekend: parts ordered from Audi dealer before about 2pm usually arrive the next day.


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## Lilblonde1993 (May 14, 2016)

I know this is a silly question but are there any instructions on how to remove the trim behind the seat.

Thanks in advance


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## brittan (May 18, 2007)

This is for removing the panel without unbolting the seat belts:

Removing
- Move both seats forwards and fold backrest forwards.
Note
Do not completely remove back panel trim; just move it aside.
Unfasten back panel trim (without detaching seat belts from outer
belt end fittings) ⇒ page 213 and put back panel trim to one side.
- Remove cover -1- from centre storage compartment -3-.
- Open lid -2- of centre storage compartment -3-.
- Starting at the top, unclip back panel side trim -4- from back
panel using removal wedge -3409- .
- Unplug connector at rear left treble loudspeaker -R14- and/or
rear right treble loudspeaker -R16- ⇒ Communication; Rep.
gr. 91 .
Installing
Install in reverse order of removal. Observe the following:

Note
♦ If the clips for the trim have been left behind in the mounting
points on the body, remove them and insert them in the trim.
♦ Check the clips for damage or deformation and renew them if
necessary.
♦ Floor covering -5- and centre storage compartment -3- must
be installed. Lid -2- of centre storage compartment must be
opened.
- Hook locking lugs ⇒ Item 12 (page 208) of back panel side trim
-4- into centre storage compartment and clip trim onto back
panel.
- Engage back panel side trim with centre storage compartment
when installing cover -1-.
- Fold lip of door seal over back panel side trim.


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## Lilblonde1993 (May 14, 2016)

Thanks for taking the time to reply

I presume I need to order the trim removal wedge otherwise my dad might break it?


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## brittan (May 18, 2007)

Cheaper better removal tool from ebay, Halfords or most other car spares places. 
eg: http://www.ebay.co.uk/itm/5pcs-Car-Door ... xyMZVTjx8F

Improvise if necessary. If you use a metal tool of some sort, wrap it in a cloth.


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## TT-driver (Sep 14, 2010)

brittan said:


> I'd have to trawl through the book to be certain but I'd expect the 'stop' signal to the fuel pump to come from the ignition switch rather than the door. Hence I'd go with the control unit.


There's a fuel pressure sensor in the engine bay, measuring the 'low' pressure. I'd expect that once the required pressure for starting is reached, the pump is switched off. The pump switches off without touching the ignition switch.


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## brittan (May 18, 2007)

TT-driver said:


> brittan said:
> 
> 
> > I'd have to trawl through the book to be certain but I'd expect the 'stop' signal to the fuel pump to come from the ignition switch rather than the door. Hence I'd go with the control unit.
> ...


Hmmm, I thought that the in-tank pump ran continuously with the low pressure being regulated by the relief valve incorporated on the fuel filter, with excess fuel being retuned to the tank.


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## TT-driver (Sep 14, 2010)

Unlocking the door and opening it, triggers the pump for just 2-3 seconds. 
Now if that is a timer or a genuine priming the system to a certain pressure, that I'm not 100% sure about.

The self study program says:

The Fuel Pump Control Module J538 controls the Transfer Fuel Pump G6 by means of a pulse-width modulated signal (PWM). The control module regulates pressure in the low pressure fuel system from 7.3-72.5 psi (0.5-5 bar). The pressure is increased to 94.3 psi (6.5 bar) during hot or cold startups.

Advantages
• Less power used because the fuel pump only provides the amount of fuel required by the engine
• Lower fuel temperature because only as much fuel is compressed as is required by the engine
• Lower noise levels, especially at idle


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## brittan (May 18, 2007)

Ah, OK. 

When I said "'stop' signal to the fuel pump" I meant when you park up and switch off the engine. What tells the pump not to pump any more? Signal from ignition switch was my thought. That signal could come from opening the door but that's illogical.


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## TT-driver (Sep 14, 2010)

The door switch is just to trigger the pump to increase the fuel pressure, leading to a faster start. If one opens the door a few times in a short time frame, the pump isn't switched on any more to protect itself.

Switching off the engine indeed switches off the fuel pump too. Basically back to a stand by modus.


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## brittan (May 18, 2007)

Thanks. [smiley=thumbsup.gif] 
I'd previously said _"I'd have to trawl through the book to be certain but I'd expect the 'stop' signal to the fuel pump to come from the ignition switch . . "_ just wanted to be sure that I was expecting correctly.

SSP downloaded, time for some homework.


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## Lilblonde1993 (May 14, 2016)

Thanks for the replys 
Waiting to take to the garage

So p3045 error doesn't mean it's a faulty control module? It could be the sensor in the engine bay?
Is there anyway to test this guys?


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## Lilblonde1993 (May 14, 2016)

Also I have been told by the garage to pay for another diagnostic test, is the Vag test more informative than Bosch?


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## TT-driver (Sep 14, 2010)

It seems we lack a bit of experience on this error code in the ********-Garage. I haven't found all of the logic regarding the control unit yet. So what data/sensor input it uses to decide what it should be doing isn't crystal clear yet.
The control unit can be checked with the Audi 'Computer system'. But that's not of much use for you now.

I might be on a wrong track regarding the fuel pressure sensor. But since a new fuel pump requires adaptation (using the low fuel pressure sensor input) I think they are related.

The readings of the fuel pressure sensor can be checked with a VAGCOM (special read out software):

Checking Fuel Pressure

Prerequisites:

Ignition ON
Engine ON (Idle)
System voltage at least 11.0 V.
Coolant Temperature at least 80 °C

[Select]
[01 - Engine]
[Meas. Blocks - 08]
Group 103
[Go!]
Field 1: Fuel Pressure (Low), Specification: 2800...7200 mbar
Field 2: Fuel Pump Adaptation, Specification: -1000...+1000 %

Group 106
[Go!]
Field 2: Fuel Rail,Pressure (actual): 55% or below is normal at idle

55% to 60% is a gray area, it may be okay, but may indicate a problem
Above 60% implies there is a failure or restriction
Causes of low pressure can include kinks or restrictions in fuel lines
Fuel filter issues including restricted/clogged or incorrect part number
Failing lift pump in fuel tank. We have seen numerous cases of sub-standard quality "factory" replacements in "factory boxes" that were obtained from aftermarket sources and are not sourced from official dealers. This led to troubleshooting problems that were solved by installing correct factory parts. We encourage customers to only install lift pump and fuel filter sourced directly from a VW/Audi dealer.


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## Lilblonde1993 (May 14, 2016)

TT-driver said:


> It seems we lack a bit of experience on this error code in the ********-Garage. I haven't found all of the logic regarding the control unit yet. So what data/sensor input it uses to decide what it should be doing isn't crystal clear yet.
> The control unit can be checked with the Audi 'Computer system'. But that's not of much use for you now.
> 
> I might be on a wrong track regarding the fuel pressure sensor. But since a new fuel pump requires adaptation (using the low fuel pressure sensor input) I think they are related.
> ...


So it's worth me paying for the VAG test,
Will the results determine if I need to get a new control module?

From the research I have done, it generally seems that if the control unit is defective it results in stalling etc as opposed to being constantly on.

I will pay for a VAG test as long as there not just going to tell me the same error code

Thanks for taking the time to reply


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## TT-driver (Sep 14, 2010)

Lilblonde1993 said:


> So it's worth me paying for the VAG test,
> Will the results determine if I need to get a new control module?
> From the research I have done, it generally seems that if the control unit is defective it results in stalling etc as opposed to being constantly on.


You're welcome. I indeed read the same when it comes to a defective unit.

Is it worth paying for the test? Hard to tell. It really depends on the person who operates the equipment. Not all Audi mechanics know the Audi Technik inside and out and therefore lack the Vorsprung. If you see what I mean. If the mechanic doesn't know all systems, sensors and what have you and how they all work together, the result might be that the automatic fault guiding system leads to replacing one bit.... ignoring the fact that is was just acting up because of some other bit delivering faulty output.

In the stickies you'll find a topic of VAGCOM users. Perhaps there's one close by who's willing to read the various measurement blocks. That might just rule out the fuel pressure issue.

My plan of attack would be that: confirm if the pressure is reached by reading the measurement blocks. If not perhaps replace the fuel filter and check again, especially if the car wasn't running 100% perfect. And or check the connectors and wiring and or a light tap onto the sensor itself, in case its internals are stuck. 
If pressure is reached, replace the control unit.

But that all is just me and I'm not a professional mechanic.


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## lebarx (Nov 19, 2016)

Hi, did you finally find the solution to this P3045 issue?

I tried to start my TT the other day, initially it fired up for around 5 secs then died with the EPC light showing up. I tried again for a number of times and the engine just tries to fire up but dies.
I ran a check with my cheapo OBD test unit and got the code P3045 (Fuel Pump Electronics faulty)


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