No turbo boost on 2000 Jetta TDI

Hey, I'm a newbie mechanic, and don't have a whole lot of experience under my belt in this field, and I need some help with diagnosing a major problem I've been having with my old jetta.

About a month ago, I started experiencing problems with the turbo, where at times it didn't seem to activate at all, or was inhibiting the engine's performance. It didn't happen often, but when starting from a dead stop, the engine felt like it was in limp mode, except that you could still accelerate in it, it just took a lot of time. Additionally, unplugging the MAF sensor would fix the problem.

After doing a bit of reading on here, combined with taking it in to have the check engine lights examined, I determined that the MAF sensor had gone bad, and after a while waiting for it to come in, managed to get a replacement installed. The problem wasn't fixed, however, only mitigated. The engine wouldn't feel as sluggish with the MAF sensor plugged in as it did before, but the car still performs better with the sensor unplugged.

Taking it in to the auto store, I got it's engine codes scanned again, and it produced these codes.

P1562: Quantity Adjuster Upper Stop Value
P0380: Glow Plug Heater Circuit "A"
P1144: Mass Air Flow Sensor Open/Short To Ground
P1556: Charge Pressure Negative Deviation

My gut is saying that some of this has to do with the MAF sensor in some way, because performance still decreases a bit when it's plugged in, and there have been reports of it causing problems with boosting, but I don't know for certain, and I haven't been doing this sort of repair work for more then a few months.

Any help people can provide would be greatly appreciated, telling me whether you think it's the MAF sensor and the electrical, or if the problem is actually in the turbo. If you guys have any questions about the car's performance, I'll do my best to answer them. Thank you!

Based on how you posted the codes I assume you went to the local parts house. It gives a starting point, however, leaves a lot of possible codes that can't be read with their scanners.
The upper limit reached is about the fuel pump and the boost deviation is about boost.
Make sure you check all the boost hoses and ensure they're connected and have no holes causing the negative deviation.
I want to say clear the codes, but, you should find a VagCom to get all the codes first.

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Well, can't say you're wrong. Pretty much the first thing I did is take it to an auto parts store to get the codes. I'll see about hunting down and checking the boost hoses tomorrow, though.

Anyways, question in regards to your comment about getting a VagCom. Would you recommend I go to a dealership to get those codes scanned, or get the software myself?

Thanks for the prompt reply, I likely wouldn't have come up with the boost hoses until much later, and the bit about the VagCom, probably never.

Mine overboosts, I’ll trade ya. Maybe you actuator is getting stuck in the no boost zone, those turbos get gunked up with carbon. https://m.youtube.com/watch?v=Ppif4qC560U

I'll add that to the list of things to check, thanks.

Honestly, it's not cheap to get the stealership to pull codes, and they're Not known to be there best diagnostics people.

I own my own cable and they're pretty much required to work on these cars. Anyone here will tell you to buy one. It's a learning curve to work on a TDI even knowing a good but about engines. The quickest way to get it fixed is gonna a local guru (trusted mechanic) in the list and have them diagnose it. It'll be cheaper than the dealer and if you find the right one he'll tell you a good bit about the car while he's at it. Tips and tricks, etc....

Search alot below
https://cse.google.com/cse?q=+&cx=018097697432185261444:_idbzjdyxdm

And check this out

https://forums.tdiclub.com/showthread.php?t=290286
https://www.youtube.com/watch?v=Ppif4qC560U

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Alright, in that case, I'm more inclined to get my own cable. I'll definitely see if there are any gurus nearby that I could have look at it, though. Thank you very much for those links, as they were very informative. Might have to set a weekend aside to pull out the turbo, and see if there's any buildup inside of it, or if the vacuum hose to it has sprung a leak.

Keep an eye out for a cable in the for sale section, they come through every now and then, I'd look for an older unlimited vin one.

Eddie is right about thinking you know cars and engines and then you get a TDI because after all how hard can it be...wow is that a humbling experience. I had a local guy that knew VWs and he had a friend that knew TDIs but most of my help has come from here or YouTube.

Also I try to support idparts, they have a guy on here that's a huge mk4 guy and has some really awesome advise, insight and experience. And they sell the good parts at very competitive prices and you won't wait days and days for "processing". It gets from wherever they are in New England to my door in Nashville Arkansas in 4 days usually... sometimes 5 days.

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My turbo started acting funny, idiot light came on and limp mode. Cycled off and back on at a light and it didn’t correct as it did for the overboost code. Drove a few miles to Advanced and it’s p1556 this time. Turbo was kicking in and cutting out, black smoke. I believe the turbo is a Garrett vnt-15, IDparts has the vnt-17 kit for $840. Any members have a used, reman or new they want to sell?

Interesting idea, the turbo line to the ecu/ ecu boost line failure.
https://youtu.be/vjcOdlUkaY8

IdiotWithAWrench said:

Alright, in that case, I'm more inclined to get my own cable.

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Check: https://www.ross-tech.com/
VCDS Lite is free for download and will do most of what you need including reading the codes.
You will need a laptop.
I registered the lite version so I could use the timing scope for timing belt changes.

Finding a OBD cable that works with it may be a challenge.
The inexpensive ones may not work.
They do have a cable that includes the full VCDS for $200.

IdiotWithAWrench said:

Alright, in that case, I'm more inclined to get my own cable. I'll definitely see if there are any gurus nearby that I could have look at it, though. Thank you very much for those links, as they were very informative. Might have to set a weekend aside to pull out the turbo, and see if there's any buildup inside of it, or if the vacuum hose to it has sprung a leak.

Click to expand...

If you are still looking for a cable I know some one who has one for sale. Its a Ross-Tech Key-USB Dual K

My first choice would be to check and make sure your actuator is moving properly in full range, those do go bad over time and stick. Check pancake pipe connection, and upper inter-cooler connections. Could be N75 valve, maybe switch out the N75 for the N18 and see if it makes any difference. Possibly be your MAP sensor but those are not a common thing to go out.

Check the hose on the left side of the engine coming from the intercooler to the intake manifold for splits on the underside of the hose. Happened to me 7 years ago and all mechanics who looked at the problem said I needed a new turbo. Happily a trusted mechanic diagnosed it in less than a minute noticing an oil sheen on the left inside wheel well. Good luck.

Hey Guys, thanks for your patience, I've been having a busy week and a half. I went ahead and replaced all of the vacuum hoses, they all looked to be the original ones that came with the car, and the boost improved tremendously, even more so with the MAF sensor plugged in.

It's still flagging the quantity adjuster code, which is strange since I replaced the fuel pump first, but it's still running well, so I'm probably going to leave it for a while.

Beyond that, it's still flagging some electrical problems all over the place, but most of those don't seem to be causing problems, and they're not really something I have the time to chase down at the moment. Wanted to thank you guys for all of your help though! If this had been a bigger problem, some of what you were suggesting would've likely saved me a lot of time and hassle.

IdiotWithAWrench said:

It's still flagging the quantity adjuster code, which is strange since I replaced the fuel pump first, but it's still running well, so I'm probably going to leave it for a while.

Beyond that, it's still flagging some electrical problems all over the place, but most of those don't seem to be causing problems, and they're not really something I have the time to chase down at the moment.

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The last paragraph gives me more info.
If you have other electrical issues they may all be tied to the P1562

Bad ground, frayed wires, broken wires or such.
See the 2nd possible below.
From the Ross Tech site:

Possible Causes
Fuse(s) faulty
-=> Wiring and/or Connector(s) from/to Quantity Adjuster (N146) faulty <=-
Quantity Adjuster (N146) not adjusted
Quantity Adjuster (N146) blocked/faulty

The fuses are all good, but I'll do some research to see how to adjust the quantity adjuster, and figure out how to tell if it's not adjusted right.

If you think the codes would provide use, I could post what all VCDS flagged.

The codes might help, especially if the components all use common grounds or power.
I did see the codes in message 1, were there others?

Before you adjust the quantity adjuster post the codes.
It should have been adjusted at the factory correctly.
If it's dirty or worn inside that's another story.

I think you indicated "I replaced the fuel pump first"
I assume you mean the injector pump.
Two with quantity adjuster problems?
I'm doubtfull.

Last, with the fuses, did you check ohm resistance, voltage on each side, or look at them?
I read about inexpensive fuses that the element inside cracks and it may not be visable.

I just looked at the fuses, but I'll see about the ohm resistance and voltage on each side when I can.

As for the fuel pump question, I meant the fuel pump that's by the fuel tank, the one you have to access through the back seats. The fuel injector pump is a bit outside my skill and budget range at the moment.

Anyways, here are the codes that are currently flagging.

Engine:

1 Fault Found:
17970 - Quantity Adjuster (N146)
P1562 - 35-00 - Upper Limit Reached

Airbags:
2 Faults Found:
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent

Instruments:
1 Fault Found:
01176 - Key
07-10 - Signal too Low - Intermittent

Central Conv.
1 Fault Found:
00912 - Window Regulator Switch; Front Left (E40)
27-10 - Implausible Signal - Intermittent

Radio:

1 Fault Found:
65535 - Internal Control Module Memory Error
00-10 - - - Intermittent

IdiotWithAWrench said:

I just looked at the fuses, but I'll see about the ohm resistance and voltage on each side when I can.

As for the fuel pump question, I meant the fuel pump that's by the fuel tank, the one you have to access through the back seats. The fuel injector pump is a bit outside my skill and budget range at the moment.

Anyways, here are the codes that are currently flagging.

Engine:

1 Fault Found:
17970 - Quantity Adjuster (N146)
P1562 - 35-00 - Upper Limit Reached

Airbags:
2 Faults Found:
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent

Instruments:
1 Fault Found:
01176 - Key
07-10 - Signal too Low - Intermittent

Central Conv.
1 Fault Found:
00912 - Window Regulator Switch; Front Left (E40)
27-10 - Implausible Signal - Intermittent

Radio:

1 Fault Found:
65535 - Internal Control Module Memory Error
00-10 - - - Intermittent

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I might have missed something but on your fuel pump in tank unless you or someone added one you don’t have a pump in your tank it’s just a pick up with a fuel gauge sensor

Have you cleared your codes first to see what codes comes back ?


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Yeah, those are the codes that remain.

I'd start here then search the next.
http://wiki.ross-tech.com/wiki/index.php/01317

Search
https://cse.google.com/cse?q=+&cx=018097697432185261444:_idbzjdyxdm

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