'06 Audi A3 2.0 Tdi 170 BMN P1269 Implausible Signal / P1266 Implausible Signal

**mcmurray** · 04-06-2019,08:32 AM

Hi all,

So I recently bought this car with running problems - it had a lumpy idle, no power, was smoky and cut out. Scanned it with VCDS and it came up the P1269 implausible signal from injector no 4.
I thought I'd got to the bottom of this as after I changed injector no 4 it seemed to be idling better so I set about doing the rest of the jobs it needed doing - without test driving it (rubbish idea). As soon as I drove it it was pretty much the same as before, no power then cutting out, struggling to start and a lumpy idle. So I scanned it with VCDS again and now it's coming up with P1266 Implausible Signal from Injector no 3! Has anyone got any thoughts on why the problem seems to have moved to a different cylinder? I've tried two different wiring harnesses and I'm pretty much out of ideas

**Crasher** · 04-06-2019,03:48 PM

The BMN engine is a PITA for running problems, the injectors were also part of the same (expired) "Campaign" on the Passat years ago. before you plough any more money in, make sure the DPF is still there as often it has been removed and over the years I have known lots of BMN's to stink. I have even had a few that were still with the DPF and they stink, it is not a good engine.

**mcmurray** · 07-06-2019,08:03 AM

Thanks for your reply, I'm beginning to regret getting something with a BMN in now - it seems to be running better now it's got a full tank of fuel so I'm not sure whether the in tank pump is dodgy or the fuel that was left in it was dodgy. You're right though, the dpf has been cut open so that partly explains the smell! The engine starts, idles well and revs freely now but there's absolutely nothing coming from the turbo, a new actuator has been fitted by the previous owner and it appears the wiring has been 'checked' (bits and pieces of the protective casing have been removed on all sorts of wires to presumably check for damage). The actuator arm moves freely by hand but what else can I check in terms of the actuator / turbo? I'm not getting any codes on VCDS now.

**Crasher** · 07-06-2019,10:08 AM

The first thing you must consider is that you cannot get a legal MOT with the car as it is so you need to deal with this before putting any more money into the car. Check the lift pump runs, delivers fuel and very importantly, the fuel lines are the correct way around on the sender top. I see this a lot and the key clue is it runs better with a full tank. Fed is black, blue is return, the sender top has annotation to show which is which.

**mcmurray** · 07-06-2019,01:58 PM

So I've checked the lift pump, all seems well - I took it apart to clean and there was a bit of crud in there, not an excessive amount though and the fine gauze was pretty clean. It is a bit concerning it's running so well now just because it's got a full tank, the fuel filter has also been replaced recently by the way. So at the moment I've basically got a non turbo 2.0tdi, well that's what it drives like anyway. What's the first port of call for troubleshooting that on these? Is there something I can check with vcds?

**Crasher** · 07-06-2019,03:16 PM

Yes, you can check the operation of the actuator movement and the N75 valve, the functions will come up in the menus of basic settings and output tests. Also apply a vacuum to the tandem pump servo hose connection 3mm pipe, you should not be able to draw air through this, it should hold a vacuum.

**mcmurray** · 13-06-2019,04:43 PM

I've had a good look through vcds and can't find those functions - basic settings just gives me basic infomation about the actuator and when I turn the basic settings on the values just stay the same. On output tests it only lets me go through a series of sequencial tests, none of which are n75 / actuator related. Sorry for the lack of basic vcds knowledge but I'm fairly new to it. The tandem pump holds a vacuum.

**Crasher** · 13-06-2019,05:34 PM

With it idling, go into basic settings group 011 if it will allow a direct number entry, if it works this should lift the idle to 1200 ish and cycle the N75 valve off and on about every 20 seconds so you can watch the turbo actuator lever.

**mcmurray** · 14-06-2019,08:36 AM

Ran the test, the idle increased and it seems to run through ok but there’s no actuator lever movement at all.

**Crasher** · 14-06-2019,11:22 AM

Put it back into Basic Settings 011 and this time, disconnect the vacuum pipe and see if a vacuum is there when the screen shows it should be. If there is no vacuum, check there is a vacuum at connection P1 of the solenoid valve block, and that a vacuum is there when indicated from P6. If a vacuum goes in and none comes out when indicated on the screen then the likely cause is the valve block is faulty.