Sons car in limp mode

bootlogic100

New member
Joined
Jun 8, 2022
Location
Secor
TDI
2005 VW Passat TDI 2.0
My son has a 2005 Passat 2.0 TDI. Ran great until 2 weeks ago. He lost power going up hills which it seems is going into limp mode. I pulled the codes with my ObdLink.

Engine codes:
P0671 - Cylinder 1 Glow Plug Circuit
P0672 - Cylinder 2 Glow Plug Circuit
P0673 - Cylinder 3 Glow Plug Circuit
P0674 - Cylinder 4 Glow Plug Circuit
P0299 - Boost Pressure Regulation Control Range Not Reached
P2108 Throttle Actuator Control Module Performance

My son says the codes that were on there when he bought it were P0673 and P2108. I don't know when the other codes were set and if they have anything to do with the Limp mode.

I cleared the codes.
He had overfilled the engine oil a bit (not sure how much but probably right past the bend in the dipstic right before it went into limp mode. I looked up and it looked like that was not a good thing so we suctioned out some. He then proceeded to drive it probably another 120 miles before it went into limp mode again.
Not knowing much about diesel engines and turbo boosters I started reading and watching videos.

All the same codes are still there.
I bought a hand pump (mityvac) and we hooked into tube going into turbo solenoid and tested the vacuum pump. That seemed good although if we wiggled the hose at the T or where it went into the vacuum pump it would drop it a bit. Didn't seem like great connections but was still pulling 20-25 hg consistently.

We then hooked up to the tube coming from the turbo actuator (disconnected from turbo solenoid) and successfully drove the rod up and down and it held.
I still haven't tested the actual turbo solenoid as I'm not sure how to do that without buying VCDS.

I think are next task is a Boost Leak Test. Unfortunately the top 2 videos of Boost leak symptoms video and DIY boost leak tester (myturbodiesel.com) show unavailable but I think this Intercooler air intake pressure test boost leak maf P0101 2005 Volkswagen Passat TDI B5.5 BHW - YouTube shows it as well.

It seems like it could be an intermittent issue, and just trying to best determine the path we should go or if the combination of codes above point to anything.
Let me know if you have any suggestions.
 

DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
N75 valve. The actuator hold pressure and move through the whole range? Check all the vac lines also. The hard plastic one likes to break.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
My son has a 2005 Passat 2.0 TDI. Ran great until 2 weeks ago. He lost power going up hills which it seems is going into limp mode. I pulled the codes with my ObdLink.

Engine codes:
P0671 - Cylinder 1 Glow Plug Circuit
P0672 - Cylinder 2 Glow Plug Circuit
P0673 - Cylinder 3 Glow Plug Circuit
P0674 - Cylinder 4 Glow Plug Circuit
P0299 - Boost Pressure Regulation Control Range Not Reached
P2108 Throttle Actuator Control Module Performance

My son says the codes that were on there when he bought it were P0673 and P2108. I don't know when the other codes were set and if they have anything to do with the Limp mode.

I cleared the codes.
He had overfilled the engine oil a bit (not sure how much but probably right past the bend in the dipstic right before it went into limp mode. I looked up and it looked like that was not a good thing so we suctioned out some. He then proceeded to drive it probably another 120 miles before it went into limp mode again.
Not knowing much about diesel engines and turbo boosters I started reading and watching videos.

All the same codes are still there.
I bought a hand pump (mityvac) and we hooked into tube going into turbo solenoid and tested the vacuum pump. That seemed good although if we wiggled the hose at the T or where it went into the vacuum pump it would drop it a bit. Didn't seem like great connections but was still pulling 20-25 hg consistently.

We then hooked up to the tube coming from the turbo actuator (disconnected from turbo solenoid) and successfully drove the rod up and down and it held.
I still haven't tested the actual turbo solenoid as I'm not sure how to do that without buying VCDS.

I think are next task is a Boost Leak Test. Unfortunately the top 2 videos of Boost leak symptoms video and DIY boost leak tester (myturbodiesel.com) show unavailable but I think this Intercooler air intake pressure test boost leak maf P0101 2005 Volkswagen Passat TDI B5.5 BHW - YouTube shows it as well.

It seems like it could be an intermittent issue, and just trying to best determine the path we should go or if the combination of codes above point to anything.
Let me know if you have any suggestions.
Ooh fun! A few things to check...
1-boost leaks. (Most common)
2-vaccum leaks (sounds like you may have checked this already)
3-Stuck egr valve
4- worn cam (also common issue)
 

auntulna

Veteran Member
Joined
Mar 13, 2005
Location
Springfield, MO
TDI
05 GLS Passat wagon, mit panzer plate
Went through in my owner days and it's a common problem with this car. You've got to inspect the fat charge air hoses, from the turbo to the hard pipe, and the 90 degree hose at the top of the motor. Those are the most common offenders. It can be a small hole or split.
 

Spring1898

Veteran Member
Joined
Feb 25, 2014
Location
US
Given that it is able to drive and not consistently go into limp mode, I would not suspect the charge air hoses as the culprits. If you are pushing 15-20psi and they are failing to the point of insufficient boost, the blow off should be evident audibly and continuously.

I would be more suspicious of the vacuum to the turbo or from the N75. What are the PSI's when the turbo actuator starts to move and when it stops moving?

How many miles on the rig? Assuming the arm is moving up and down along its total range, and at the right PSI's, the interface between the linkage and the vanes might be worn out.

Or it could be that the vanes are carbon'd up. When was the last time it got a good 'Italian' tune up?

Or the intake could be so clogged from the EGR it is not able to draw in sufficient boost, but this is less likely.

BUT First, has the air filter/snow screen been cleaned recently?
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds

P0299 is the code that’s giving you the problem. I had this a month or so ago, my turbo actuator was not holding vacuum. Replaced the actuator and all has been good since.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Probably not the n75 valve. Everyone and their dog throw that at a p0299 as the first part to try, and yes they can fail, but not as likely as the other issues.
 

bootlogic100

New member
Joined
Jun 8, 2022
Location
Secor
TDI
2005 VW Passat TDI 2.0
Thank you for all the responses. I think this gives us a few ideas to go on. It appears the turbo actuator holds vacuum and starts movement at 3 hg and ends at 17 if I remember right. It was whatever a forum post said it should. The n75 can be had for not to much money and worth a try I guess. We also need to do that boost leak test which is next on agenda.

it has 250,000 miles on it.

thanks for all your help on will hopefully land on something soon.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Thank you for all the responses. I think this gives us a few ideas to go on. It appears the turbo actuator holds vacuum and starts movement at 3 hg and ends at 17 if I remember right. It was whatever a forum post said it should. The n75 can be had for not to much money and worth a try I guess. We also need to do that boost leak test which is next on agenda.

it has 250,000 miles on it.

thanks for all your help on will hopefully land on something soon.
Before spending the money on an n75 valve (btw, only get oem ones of them...) pull the valve cover off and look at the cam.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
2nd that, pull the valve cover and inspect the cam. Look at the cam lobes, on a PD they are buried, you are looking for a chamfer all the way around each side of each cam lobe. If the chamfer is missing and/or sharp edges are present you will need to replace your cam.
 

Tom in PT

Veteran Member
Joined
Jun 7, 2017
Location
Twilight Zone, WA State
TDI
2005 Passat sedan - SOLD; 2013 Passat DSG; both purchased new
After you inspect the cam lobes I would inspect the boost hoses as recommended by auntulna in post 4 next. On some of these cars there is a ground wire that chafes through the lower hose. Pull off the belly pan and look up from the passenger side at the large rubber hose and inspect it carefully.
 
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