A2 1.4 tdi limp mode

stevec

stevec

Member
Wales
Hi All
Over the past couple of weeks been having an annoying problem with my A2. It seems as if someone has disconnected the turbo and the car accelerates REALLY slowly. After turning the ignition off and back on again car behaves perfectly. Had the car's diagnostics interrogated and the following code pops up.
DTC 17965 charge pressure control: Positive deviation: P1557.
Having read previous threads could the fault lie with the N75 valve/hoses or intercooler?
If so does anyone know the part number for the N75 valve just in case i have to order new? Car's engine code is AMF and is an 2001 model
Thanks
Steve
P.s.
Great site
 
A2 Limp mode

Hi All
Looks like it's the outlet boost hose directly from the turbo. A lot of oil around the area. Is there a seal there or does the hose make the seal?
Thanks all
Steve
 
Hi Steve
The hose makes the seal - there are no replaceable O rings or seals etc

Cheers Spike
 
As you have found your leak I would still recommend you to take a close look at the pressurized hose coming from the inter cooler.

On the AMF in particular the hose meats up with the larger hose coming from the air filter and it wear against the clamps close to the webasto heater. Make sure those clamps are not twisted against the pressurized hose as it digs in in just a few miles. You will hear a surge while driving when the turbo pressure comes and it feels like the clutch is slipping.

There is also a good protector you can build yourself and you can clearly see it here:
http://www.a2oc.net/pictures/watermark.php?file=470
(Look just over the a2oc logo)

Scotch will not help as a temporary fix since the pressure is high so the only fix requires a good garage with good hardware in store. You can cut the hose in two. Make an insert out of an alu tube that fits perfectly inside the hose. Preferably turn a few groves in a lathe so the clamps on each side gets a good grip.

BTW, in later engine models Audi routed the pressure hose on the other side of the engine.
 
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I too have a very similar intermittent 'Limp' problem when cold which has become more frequent in the last month. Car booked into Harrogate audi next week ( it's still under warranty!):)
 
Audi Harrogate refused to deal with this as a warranty item and charged £95 for telling me there is nothing showing on diagnostics. Same problem again yesterday afternoon......:mad:

Not sure what to do next:confused:
 
Re Limp mode

Hi
Since pressure will take the easiest path i will have to sort out this leak first before i search for anymore. But point noted. There is in fact an 'O' ring seal from the turbo to the first boost hose.
Audi part number 8zo 129 646 and they are about £0.95 each.(special order though) nice shade of silver.
Try vag cat for break down of system with part numbers.
If you remove engine undertray, turbo is visible and you can inspect for leaks. Awkward to get to would suggest garage or pit. Since i've 'wiggled' mine to ensure hose had a good seal, fault has not occured. But will change anyway when weather improves!(come to sunny Wales)
Steve
 
hi Steve
just pull the tray off and look at the turbo from underneath. Check all the little hoses near the waste gate as they can come apart where the flexible small bore pipes slip over the rigid pipes and this can cause what you are experiencing. It happened to me and drove me mad but was an easy fix when i discovered it.
Hope this helps
 
Well, its nice to hear someone else is experiencing this annoying problem... but my A2 seems to get far worse in very wet weather, has the rain got anything to do with this fault does anyone know? as I nearly came to a stop going up a long hill on my way home, it was a hazard lights occasion!
Any help appreciated to this needy new comer :eek:
 
There is a slim chance that the drain hole in the air box is blocked - if this was the case, no air would be entering the engine.

I've never heard of an A2 with this fault, but it is pretty common on older A4s.

Either way, you'll need to remove the undertray, so whilst you're checking for split or loose pipes, undo the air filter housing and check that too.

Cheers,

Mike

PS, Also, check in the compartment in the passenger footwell, under the carpet and the aluminium cover - there may be water in there.
 
stevec said:
Hi
There is in fact an 'O' ring seal from the turbo to the first boost hose.
Audi part number 8zo 129 646 and they are about £0.95 each.(special order though) nice shade of silver.
Steve
Click to expand...

Hi Steve
Thought I must have missed it first time around so I checked the aftercooler parts diagm again (illustration 145.55) but still could not identify this O.ring. Can you download the illustration for future ref for other club members

Cheers Spike
 
Thanks for the picture Mike.

Steve, That particular O.ring is on the air cleaner (suction) side of the turbo. It certainly needs to be in good condition to prevent dirty air being drawn into the turbo but it won't cause a loss of boost pressure.

The only thing it would do is allow the engine to draw in air which was not measured by the MAF sensor. Not sure what the effect would be on engine power as unlike petrol engines, diesels don't need a precise air/fuel ratio for combustion.

Cheers Spike
 
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Re Audi A2 limp mode

Hi Spike
Thanks for the info. Sorry should have said INLET hose. Since i wiggled the pipe(to make sure seal was good) A2 hasn't cut out since?? I wiped off excess oil from around the area, when weather has improved?? will have another look to see if there is any more oil there. Hope this would cure the problem as i cannot see any other leaks from the system. The only other thing it could be is a faulty n75 valve?
Got this from a guy how has a vag com account.

17965/P1557/005463 - Charge Pressure Control: Positive Deviation
Possible Symptoms
Reduced power output
Limp mode
Possible Causes
Boost Pressure too High
Hoses/Pipes incorrect connected, disconnected, blocked or leaking
Charger Pressure Control defective
VNT (variable nozzle turbo): nozzles stuck
Solenoid Valve for Boost Pressure Control (N75) defective
Possible Solutions
Check Hoses/Pipes to/between Components
Check Solenoid Valve for Boost Pressure Control (N75)
Check / Clean / Replace Charge Pressure Control
Check / Clean mechanism for variable nozzles

Would that mean all hoses? including ones feeding the turbo?
Thanks
Steve
 
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Hi Steve
My interpretation is that it means the charge air hoses after the turbo.
The solenoid and N75 valves are possibilities but also check the connecting pipes are not blocked or split as this would affect the vacuum which activates the valve.
As mentioned previously, also check the two small signal lines which go to the turbo.

As you probably know, only the 90 TDi had the variable nozzle turbo so you can discount the related issues

For future ref, most fault code info is available on the RossTech web site - http://wiki.ross-tech.com/index.php/Category:Fault_Codes

Cheers Spike
 
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