PD Underboost limp mode VCDS diagnostics tips n' tricks

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Total VCDS noob here. For the last four or five months I've been struggling to figure out why our recently acquired '04 Passat BHW will go into limp mode nearly every time we drive it around, especially on hills. I've checked all the hardware (turbo-removed and cleaned, intercooler pipes--smoked and non-leaking, EGR-deleted, MAP, MAF, N75, tandem pump all replaced), so I'm on to figuring how to run some real time diagnostics using my ridiculously expensive VCDS wireless dongle. As is Bentley's MO, there's no manual for the last few years of a chassis, just like with my Eurovan, so I'm flying blind.

Is there some kind of VCDS for Dummies primer on how one explores the diagnostic tools? I don't even know enough to run a basic search query that can tell me something about measuring blocks, etc. Lil help?
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
I know I deserve that kind of response, but I require a little more hand holding and gentle pats on the head. The VCDS website isn't very noob friendly, though I am trying to navigate to find my own information. Perpetual limp mode is a sad metaphor for my entire life.
 

DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
Listing what codes vcds comes up with might help a little more. You could be pointed in the correct direction of where to look and what to look at.
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
It's the ubiquitous P0299 underboost code that seems to afflict every BHW, which can always be resolved by fixing boost leaks except when it can't.
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Thank you, that's very helpful. Knowing what to look for is half the battle.

Now I'll slink away and read the wiki.
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
I'm having intermittent limp issues that seem to be trans related, but my generic code reader doesn't show any trans codes. When I attempt to use my VCDS Mobile reader and run an autoscan, it hangs up at 5% and then never goes beyond. If I try to just run a trans module scan it indicates that CAN failed. It won't even run a basic OBD2 scan for me any longer. It's utterly useless to me.
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
I'm not familiar with VCDS mobile, so have you tried contacting RossTech for help on the issue?
Sounds like you have some OBD port issues or wiring things to sort out since you can't communicate with the modules.
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
Sounds like they've seen this issue before with that interface
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Ugh...but mine is 9% worse. I guess I'll need to register on their site and figure out how to upload files and such.

Thanks
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
I didn't spend a lot of time looking into it, but it seems fairly "common" and could be as simple as needing to update your firmware or something... don't be such a snowflake :D
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Ha! I just plugged it into our Eurovan and autoscan and access to the TCU were just fine. Apparently this is an issue with the Passat's wiring system. Not sure what to do about that.
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
There you go.... time to obtain wiring diagrams and learn how to read them..... fun times ahead!
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
Actually, I just thought about this... your PORT should be ok if I understand what you've said above correctly.
Check this by going into autoscan and clicking gateway installation list.... it should provide clues of the potential wiring\module issues that can't be reached.


That way, you can start your wiring checks at those respective connectors\modules.
If my theory is correct, you should be able to run diagnostics\communicate with some of the individual modules, but not the ones that you're having issues with.

Since the slushbox is near the top of the list, it would make sense that it hangs\crashes early in the process (5% or whatever).
 

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,
Also, what do you have for a slushbox? 09A EEN or EYF possibly?
Being that it's an 04 Passat, it would be a gmr zf5hp transmission.
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Ah ok, it makes sense that it's hanging at the transition from the engine to the trans. It hasn't always done this, but it's been pretty consistent lately. I should say that back when it wasn't doing this, the car was going into limp mode nearly every time we drove it. Now it only does it randomly and far less often.
 

TurboABA

Top Post Dawg
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
I'd say he needs to examine\focus on the TCM (J217) 88pin connector and harness since he can't seem to reach it with VCDS (supposedly... since we haven't had confirmation of failed communication from the VCDS tool as requested in #17 above..... but it seems feasible).

Once we know what the TCM is reporting, we can suggest what else needs digging into.
 

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,
I'd say he needs to examine\focus on the TCM (J217) 88pin connector and harness since he can't seem to reach it with VCDS (supposedly... since we haven't had confirmation of failed communication from the VCDS tool as requested in #17 above..... but it seems feasible).

Once we know what the TCM is reporting, we can suggest what else needs digging into.
Which means that he should pull the TCM out and check for water damage.
It's under the passenger side floorboard, you can get to it without removing the front seat by pulling the side trim out and lifting the carpet up and then there's a black box in there that you pull up to release from the clips and pull it out. Open that box and the TCM is in there.
I will link my thread from when I had TCM connection issues. I learned a ton through that.
 

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,
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Thanks for that link ^^^

I'll try and run that VCDS procedure in #17 this weekend and report back. I checked my TCM a few weeks back, and there was no sign of ever having water intrusion into the plastic case. As per the aforementioned link, I might need to pull the module out and have a peek inside the metal case, as well as run some resistance tests.
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
Hey MZQR, in your link you mentioned using VW's diagnostic flow charts. Is this from a Mk4 Bentley or some other source?
 

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,
Hey MZQR, in your link you mentioned using VW's diagnostic flow charts. Is this from a Mk4 Bentley or some other source?
I got that from Mitchell prodemand or identifix, I don't remember which one I got the flow charts from.
Are you getting no communication to TCM codes?
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
So I dragged my laptop out and used the VCDS cord to run an autoscan. I did this because the mobile feature refused to log in.
I tried to run the Gateway Installation, but it just said gateway does not respond. I was able to see the TCM, which had no codes. I did an output test and could hear solenoids clicking, so communication doesn't seem to be the issue.
 

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,
So I dragged my laptop out and used the VCDS cord to run an autoscan. I did this because the mobile feature refused to log in.
I tried to run the Gateway Installation, but it just said gateway does not respond. I was able to see the TCM, which had no codes. I did an output test and could hear solenoids clicking, so communication doesn't seem to be the issue.
Was there any no TCM communication codes in the ecm?
 

Zeitgeist

Veteran Member
Joined
Nov 10, 2004
Location
Cascadia
TDI
'04 Variant and Vanagon mTDI
No TCM codes, but then again I probably cleared them the last time I attempted to use VCDS, and the symptoms haven't returned since then. I'll have to retry with the laptop next time the symptoms show up again. Any thoughts about why I wasn't able to call up the gateway screen?
 
Top