Hi, mines a 2012 2.0L tdi 170bhp yeti and it's going into limp mode on just about every journey, especially when cold! It keeps saying in vagcom that the actuator is stuck or else, but less often, it's saying "turbocharger boost control position sensor circuit, implausible signal".

I've replaced the actuator and the turbo vane lever moves freely without any restrictions, I've checked the lines using a vacuum gauge/pump and all were fine except there seems to be leak in the line going down behind the engine to the egr. I blocked this pipe to see if that changed anything but it neither showed an egr problem or cured my actuator problem. So that seems to be just another problem to sort at a future date!!!

I've swapped the n75 valve as well with a working one and that didn't fix it... any suggestions or anyone experienced this before? It's cfja engine,  thanks.

 

Turbow vanes sticky when cold.

 

I lived with this problem for 15 years with my MK1 Octavia, a Mr Muscle enema would bring respite for between 6 and 18 months, avoiding large throttle openings in the first few miles would avoid the limp mode and need for ignition switch rebooting.

 

Problem went away every year from mid Spring to mid Autumn and was at its worst in the coldest weather.

The vanes move really freely, today I took out the map sensor and cleaned it with an airline and cloth

Put it back in and checked the wiring all the way back to the ecu for any mouse nibbles as they had nibbled on the injector wiring previously, the engine cover foam makes lovely bedding seemingly! Anyway I found nothing out of place but after a few mins running and clearing faults out seemed to run fine and I drove it for a few miles and all is well, let's see what it's like when cold tomorrow..

 well it's still going into limp.

Any suggestions welcome

Ok so it's still saying the actuator is stuck and flashing the glow plug light, however it's always on now from about 30-50 seconds after start-up. It sometimes throws up an implausible signal code from the actuator position sensor circuit. I've put a new actuator on it (does it need to be adapted?)
I've followed the wires all the way back to the ecu and removed the ecu and cleaned everything around it, unplugged it and checked for corrosion, all good. There's an earth connection near the ecu where the cabin air intake is and I've cleaned that! I've cleaned another couple of earth points as well, one behind the washer bottle filler neck and the other in the left hand side of the chassis in front of the wheel well, all were pretty good. I've replaced the N75 solenoid as well. None of these have made a blind bit of difference!
I now have 2 working actuators and 2 working n75 valves! The egr valve diaphragm is leaking a bit and doesn't allow the flap to fully open it leaks above 10mmHg. This egr was replaced a few years back and it's a pig of a job to do and expensive so I'm not looking forward to that but in the meantime, thinking that the leak here was causing the turbo actuator to fail I blocked the vacuum pipe going to the egr but this also made no difference. As an aside, in case it matters, the satnav isn't working because the antenna is saying short to ground and the parking sensors have decided to give up as well saying the inner left one is kaput!
Any Sherlock Holmes out there able to deduce anything from all this?

 

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Edited 12 March, 20233 yr by wexti

This takes me back 2 years to the issues I had with my 1.6tdi CAYC. 

 

I've added an additive to every tank since then, injector cleaners, Archoil, the VW additive G001790M3 at least twice, I've used DPF spray cleaners about 4 times through the o2 sensor and manipulated the nozzle so lots went into the turbo, and reverse squirted through the cylinder head towards the EGR valve (dunno if it helped, but when you're cycling the ignition every few hundred yards you get desperate!)

 

Actuator is now free, I don't get limp mode, ever.

 

I have a small pile of MAF, MAP, N75 sensors, oh yea and I also cleaned the ASV of muck.

 

The car now regens well every 300 odd miles, it revs to 4500rpm, and since remapping the EGR valve out it goes really well, with real world economy around 45mpg extra rural on A & B roads. 

I am wondering if the dpf maybe is blocked. But there isn't any warning light coming on

12 hours ago, wexti said:

I am wondering if the dpf maybe is blocked. But there isn't any warning light coming on

If you have an OBDII dongle the App VAG DPF will give all the health of the DPF needed onto a smartphone.

Great idea, thanks.

Does anyone know where to get a schematic for the pins on the ecu so that I test the correct ones that go to the actuator?

Surely a vacuum test would be better to know whether the full movement of the actuator is being achieved, often due to carbon build up this doesn't happen. 

That's been done as well, full and free movement here.

Just did continuity test on the signal wire going back to the ecu (pin 58 by the way!) and it's perfect as well. I took out the air filter housing and battery tray so that I could see the loom all the way back and fiddled around with it, no change in full continuity all the way back. I'm going to try the 5v and earth wires next, anybody know where the earth wire finishes?

Ok I'll answer my own question here, the 5v goes to pin 25 and the earth goes to pin 53

So FINALLY!!

The check valve at the start of the vacuum line was the culprit, it was partially blocked and while the line does go to full vacuum, it is slow to build up and it meant the turbo actuator would be slow to move and go outside of spec. I'm guessing the failing egr cooler diaphragm (replacing this on a 4x4 is not for the faint hearted) is allowing contamination into the line and travelling all the way back to the valve and luckily building up there and not damaging the vacuum pump.

Hopefully this will all help someone else in the same boat down the line.

Edited 20 March, 20233 yr by wexti

Well done that man!

 

So, are you cleaning or replacing this part?

That is the same effect as when the hoses degrade and partially collapse from turbo heat when under heavy load.

 

That one on my 98 diesel Alhambra took a very very long time to track down, I knew it was heat related from when it happened (towing uphill on autoroutes etc) but finding the culprit was not easy.

 

Well done to you, another example where a garage would likely end up taking a customer for a fortune and never resolve the problem.

I had nothing to loose so earlier this evening I sprayed in some brake cleaner and have it a few moments then blew it with an air line. Hey presto! Good as new again.

As an aside, it had been driving for a month or more in limp mode as we needed the car every day, I suspect the egr and dpf were not able to clean themselves when in limp so I brought it to work today (sales rep) and gave it a good thrashing. It kept going into limp in the morning saying the egr was knackered but by afternoon she was good as gold.

I'm bringing it in the motorway next to regen the dpf 🤞

Edited 20 March, 20233 yr by wexti

Wiring diagram for the turbo actuator sensor if needed (g581)

G247 is the fuel rail pressure sensor

Edited 20 March, 20233 yr by wexti