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Need help with code P1288 on a 2000 Audi TT Quattro.

Replaced valve N249 but the...
Need help with code P1288 on a 2000 Audi TT Quattro. Replaced valve N249 but the code comes back. Car runs beautifully otherwise.
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Answered in 1 hour by:
11/27/2017
Matt
Matt, Engineer
Category: Audi
Satisfied Customers: 23,078
Experience: Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
Verified

Hello

to get that code this points to a fault with the bypass or 'dump' valve on the turbo inlet

the attached image shows the location of the bypass valve

typically the valve springs a leak that then that loses boost pressure and also prevents the turbo from controlling the boost pressure correctly

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Customer reply replied 5 months ago
Do you possibly have a better picture or some sort of part number?

if your's is the 225bhp model its a larger unit see here

https://audi.7zap.com/en/rdw/audi+tt+tts+coupe+roadster/att/2000-229/1/145-145077/

item 38

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Customer reply replied 5 months ago
I’ve replaced that valve as well.

OK in that case

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.
As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propaneor brake cleaner around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Air leaks are very temperature dependent as gaps can open up as things expand with temperature so depending on how the leak occurs ( on a hose joint with a clamp expansion will help seal and on a vacuum hose expansion ill make a leak worse) so leaks can be better or worse as the engine heats up.
1 vacuum leak path that you won't find with the above test is if the brake servo is leaking

so try clamping off servo hose to see if this has any effect

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Customer reply replied 5 months ago
The description of the code claims there is an electrical short to B+. Can the air leak cause this sort of code?

hello

no an air leak won't create an electrical short

the reason for mentioning that is the bypass valve is part of the measured air circuit that is all controlled by the ECU

so any leaks or uncontrolled air paths ( like a faulty bypass) will create errors

if the car has a wavering idle speed or a bit of hesistation on acceleration then these too are signs of an air leak

also the bypass valve is a mechanical item with no wiring? can you post up your code description

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Customer reply replied 5 months ago
P1288 Turbocharger bypass valve short to B+

Hello

OK can I ask what scan tool is being used here as the bypass valve on these is a mechanical device theres no electrical connection to short out?

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Customer reply replied 5 months ago
It’s a Launch tool. I myself am confused but even with another blue point code reader the same code is read.

Ok

I'm going to have to opt out here as this isn't something I've seen before

another expert will be along to help

good luck

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Wolfgang
Wolfgang, Audi master tech
Category: Audi
Satisfied Customers: 5,118
Experience: Senior Audi Master Tech 15 yrs
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Thanks for choosing Just Answer . I'm Wolfgang here to help!!

I am confident we can resolve your problem together. Please
understand that I don't know your skill level. In most cases when you have a problem
with the way the vehicle performs, specialized tooling is required to acquire computer
data/information or engine testing results. We didn’t build these complicated vehicles; we
just diagnose and fix them. Also understand that I can't see, smell, hear, or touch the
vehicle either, so it may take a few replies to get to satisfactory results. Note there may be an issue where the complexity of the issue will require a Premium Service. This service will be an addition to the normal question cost. Usually it does not come down to this but keep in mind!! I am also going to direct you with the fastest, easiest and most common things to check first. Please be
patient and permit me to do what I do best.
I also try to give all of the information you may need, expecting a “positive rating” in
return. I will also continue assisting you after you have rated me, if necessary. If there
is any reason I cannot get a positive rating, please let me know why “in advance”, so I
can go another direction for you. I am sorry you’re having this problem; I’ll help you
through it.
Below is my first answer or request for more information. If you do not understand it, or you need more information from me, or need me to go in more detail.

I do need a vin # of the vehicle to get the correct wiring diagram to assist!!

Thanks

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ok you will need a volt meter

the turbo bypass valve has a vacuum hose follow the vacuum hose to the electric valve that controls the vacuum . remove the connector and measure from pin 1 of the connector to negative battery post with the key on how many volts is that reading?

thanks

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Customer reply replied 5 months ago
Is this electric valve, valve N249?

yes correct.

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Customer reply replied 5 months ago
Hi, which is pin 1? There is a green wire and a black/white wire.
Customer reply replied 5 months ago
No voltage at either pin

the green wire should have 12 volts . now if you do not have 12 volts there go to the camshaft adjuster connector disconnect and should have a green wire there also do you have 12 volts there?

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no on the other end!!! 2 pin connector

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Customer reply replied 5 months ago
I’m sorry im not familiar with this car/motor at all. Where is this adjuster located?

ok this is the older motor go to the valve that is on the intake hose in that same pic that has that same green wire . test there

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ok what if the engine is running?

is it the same voltage?

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Customer reply replied 5 months ago
3.6-3.6 Volts. Constantly fluctuating.
Customer reply replied 5 months ago
3.4-3.6Volts**

ok remove the air cleaner and you will see a 14 pin connector . you will see a green wire . disconnect and then measure the plug that is other side of the harness going into the cabin measure the voltage there and let me know what is the voltage!!

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Pin 6 of that connector
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Customer reply replied 5 months ago
3.5 volts
There has to be a 14 pin it’s usually next to the air intake tube for the air cleaner batt may have to be loosened
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Just to make sure this is an atc engine code? If not sure options sticker in the spare tire area white sticker. Photo please
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yes !!! perfect!!

let me verify the wiring diagram to make sure!!

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ok fuse 34 of the dash fuse box left . is that fuse good and do you have 12 volts at that fuse both sides of the fuse ? to check is the fuse remains in the slot and on the top of the fuse you see a slit where the metal is exposed measure from one leg of the fuse to ground then the other and should show battery voltage on doth sides when checked!!

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Customer reply replied 5 months ago
Ok let me check

check with the key on !!

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Customer reply replied 5 months ago
12v on both sides

ok good still checking the diagram!!

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Customer reply replied 5 months ago
Ok

do you have the battery removed? please do and take a pic of the intake hose area from the bumper to where the air filter housing would be

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need further down view near the headlamp and battery area!!

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ok i need some time on this is that ok ? may run into tomorrow

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Customer reply replied 5 months ago
Of course! Appreciate all your help so far. Will be waiting to hear from you tomorrow. Thanks!

my pleasure!!

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Customer reply replied 5 months ago
Hi, just checking in.

my data base went down and trying to fix now !! if you can give me some time i will get back asap hopefully later tonight!!

sorry but i will get back!!

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Customer reply replied 5 months ago
Ok that’s fine. Just one question, have you seen this failure code before?

yes usually a wiring issue from the fuse to the solenoid . there is a splice that goes bad !!! i need the correct diagram to make sure if it is in those connectors or not (10 pin)

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Customer reply replied 5 months ago
Ok perfect! Yea I don’t want to tear apart the harness blindly! Thanks again!

hey in the right side of engine compartment is there a 14 pin connector ?

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at that solenoid one of the wires is green with a black tracer line correct?

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just want to verify the green wire in pin # 1 the housing is marked 1 and 2

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Customer reply replied 5 months ago
That’s correct

unless the 14 pin connector is the junction area from inside and out . if you pull the wipers and black cowl cover . on the left is a junction box cover black in color . remove to gain access need to find the green wire or you can tag that connector at the green wire a hot wire from battery positive to that green wire and verify that the code goes away!!! (dirty test)

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Customer reply replied 5 months ago
Will try that and report back
Customer reply replied 5 months ago
Could you kindly send me the schematic for N249?

pin 2 goes to pin 105 of the ecu small connector and the green wire comes from fuse 34 from fuse box

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no i would of told you to go there!! that is the ecm power relay and the air pump relay if equipped

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yes that is correct it will be 14 pin connector pin #6

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Customer reply replied 5 months ago
There are no 14 pin connectors here. There are 6 pin, 8 pin and 10 pin connectors. There are also no solid green wires here only green with tracers. None in pin #6 though.

there may be large pins then small pins in the same connector

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Customer reply replied 5 months ago
The white and black wire is what is broken right? I should have power there?

no the green wire !! that has to be 12 volts i really do not think you have an issue with the other wire!!

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Customer reply replied 5 months ago
Found the problem.. the connector to the coolant temp sensor had been switched with the N249 valve. N249 has a gray with a green tracer and a yellow with with a black tracer. Switched them around and code cleared itself.

great !! anything else?

if not.....

I try to be online 365 days a year.

I only earn a paycheck when a customer rates me Ok, Good, Excellent.

This rating is VERY IMPORTANT! Your rating compensates me on my time and my expertise on your issue!

A lot of the repair information and fixes are hard to come by!!

I HAVE DONE MY PART IN HELPING YOU AND I DO EXPECT THE SAME WITH A 5 STAR RATING!!!

So please rate me above!!!! Bonuses are also greatly appreciated!!!

If I have not addressed your original question to your liking yet, I hope you will reply and continue working with me, since your charged the full question value, regardless if you rate negative or not at all. If you rate me now, do not worry, you can still reply later to me.

Thanks

Wolfgang

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Customer reply replied 5 months ago
I hope you’re not tired of me but I also have the oil pressure warning coming on after long drives. Oil sender has been replaced. We have removed the oil pan and cleaned the pick up tube (which was a bit dirty) but the light comes back after a long drive.

did you pull a cam cap in the rear to see if the cap is scored?

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Customer reply replied 5 months ago
Bad sign if it’s scored I take it? I’ll check in the morning. If it is what can be done?
Replace the head and then mains and rods bearings needs to be checked
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Customer reply replied 5 months ago
What’s the oil pressure supposed to be on this engine?
Minimum 20psi warm idle
Wolfgang
Wolfgang, Audi master tech
Category: Audi
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Customer reply replied 5 months ago
Ok thanks!

my pleasure!!

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