Keep Getting underboost engine code

TwistedSmoke

Well-known member
Joined
Nov 19, 2016
Location
Milford ,Pa
TDI
03 Jetta tdi
I keep getting the underboost engine code. i check the boost tubes they all look ok. i check all the vac lines they look alittle old but not to bad. i swapped the n75 with the n18 that i had in the garage and still got the code so i dont think its the n75. Any other ideas i can check to understand what might be causing this Under boost?
 

CopaMundial

Veteran Member
Joined
Jan 30, 2011
Location
Southeastern PA
TDI
03 Jetta Wagon 5sp (New to me Oct 2014) 03 Jetta 5sp (RIP Aug 2014)
Have you checked to see if the turbo actuator goes through it's full range of travel?
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
I would physically remove fuse #34 and test it.
First thing, even though you have gone through the vacuum lines, check the amount of vacuum at it's farthest connection to see if you still have at least 20" of vacuum, if not the vacuum solenoids do crack open, but usually invisible to the naked eye.
 

TwistedSmoke

Well-known member
Joined
Nov 19, 2016
Location
Milford ,Pa
TDI
03 Jetta tdi
turbo is brand new vnt 17 So i hope its working but will jack up the car when i have a chance and check also check the vacuum down there while i am at since that is the farthest vacuum hose. thx for the info. Also just remember a buddy of mine just told me about the map sensor on the intercooler and says they can get dirty and screw up the boost reading.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
Let me say this as I know you have misunderstood my instructions.
The turbo connection is, yes, the farthest distance from the vacuum pump...
On the passenger side, over where the last solenoid is, say, the one connected to the EGR valve should still have 20"
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
If you have Vag-Com attached, you should be able log all of the request versus actual. If you can, log while you are attached to the OBDII connector; it may tell you where the issue is.
 

TwistedSmoke

Well-known member
Joined
Nov 19, 2016
Location
Milford ,Pa
TDI
03 Jetta tdi
ok will borrow my friends vag com and have him sit there as we drive and check it. i cant currently do it cause we are having a lot of bad rain up here and it sucks to drive on the windy road up here in the rain.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI
You mention it's a new turbo, where is the turbo from? Which code are you getting?
 

Tom_B

Veteran Member
Joined
Aug 24, 2004
Location
Central Oklahoma
TDI
15 Touareg, 14 A6
Underboost is often related to charge air path leaks, but there can be many possibilities. You mention the boost hoses and vacuum lines look ok, but looks don't always tell you what you need to know. It may be useful to use Canadian Grizzly's excellent summary to verify it's not a control issue, check the integrity of your vacuum system, etc. The link talks about overboost, but control problems are control problems. Good luck!
Diagnosing and Fixing Limp mode for A4 1.9TDI [low power troubleshooting] | TDIClub Forums
 

Curious Chris

Top Post Dawg
Joined
Jun 11, 2001
Location
Pineview GA
TDI
Jetta Wagon 2003 RIP Rockford IL
16683/P0299/000665 - Boost Pressure Regulation: Control Range Not Reached
Possible Symptoms
  • Reduced Power Output
  • Limp Mode
Possible Causes
  • Hoses/Pipes incorrect connected, disconnected or leaking
  • Charger Pressure Control defective
  • Turbocharger faulty
  • Diverter Valve faulty
Possible Solutions
  • Check Hoses/Pipes to/between Components
  • Check / Clean / Replace Charge Pressure Control
  • Check Turbocharger
  • Check Diverter Valve
 

TwistedSmoke

Well-known member
Joined
Nov 19, 2016
Location
Milford ,Pa
TDI
03 Jetta tdi
yea will check other part after i check it this weekend coming up with friends vag com
and no the tune is still set for stock turbo.
 
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