www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums TDIFAQ Articles Links Meets
Orders TDI Club Cards TDIFest 2014 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You



Go Back   TDIClub Forums > VW TDI Discussion Areas > TDI 101

TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

Reply
 
Thread Tools
Old August 3rd, 2010, 11:11   #1
LadiesMan217
Veteran Member
 
LadiesMan217's Avatar
 
Join Date: Feb 2009
Location: Springfield, MO
TDI(s): 2005 GLS TDI
Fuel Economy: 33mpg city
Question Bad Temp Sensor?

Hey volks, my CEL came on this morning. The code scanner came back with P0128. Now i just had my t stat replaced about 3 mo ago by "vwjettadsl". The temp gauge seems to work fine. From what ive found on the forum it seems that it could point to a bad temp sensor which i believe i read somewhere on here to be rather faulty. Could anyone shed some light on what i should do about this?
__________________
2005 Jetta GLS TDI: Reflex Silver, Black Velour, 15%tint Front, 5% Back, Gator Tuned, Ventectomy, Magnaflow High flow Cat, Aero Turbine Muffler, AFE Cold Air Intake, Philips Xtreme Power Headlights, 215/60/15 Goodyear Eagle Gt's
LadiesMan217 is offline   Reply With Quote
Old August 3rd, 2010, 17:18   #2
Jeff Heyerman
Veteran Member
 
Join Date: Apr 2007
Location: Oakville, ON
Default

Well I just went through this. If you have VCDS drive around with someone monitoring the group 00. The coolant "temp" is on that line. It goes from a high to low value as coolant gets hot. At operating temperature it should be about "74" (74 what I have no idea). Mine was fine most of the time, but then jumped erratically on occasion (3 times in 20 minute drive). Also monitor group 01, which gives coolant temp in C - should be just shy of 90C

When you get home, check coolant temp with a meat thermometer (open cap slowly). Should be 87C or so. If coolant is too cool, then prob code is from t-stat not working properly. But much more likely sensor is bad.

The one I just replaced in our 2002 was a black one - apparently notorious for failing. Also for replacement buy from VW, apparently aftermarket ones also let out the ghost quite quickly.

Cheers.
Jeff
Jeff Heyerman is offline   Reply With Quote
Old August 6th, 2010, 20:03   #3
LadiesMan217
Veteran Member
 
LadiesMan217's Avatar
 
Join Date: Feb 2009
Location: Springfield, MO
TDI(s): 2005 GLS TDI
Fuel Economy: 33mpg city
Default

Quote:
Originally Posted by Jeff Heyerman View Post
Well I just went through this. If you have VCDS drive around with someone monitoring the group 00. The coolant "temp" is on that line. It goes from a high to low value as coolant gets hot. At operating temperature it should be about "74" (74 what I have no idea). Mine was fine most of the time, but then jumped erratically on occasion (3 times in 20 minute drive). Also monitor group 01, which gives coolant temp in C - should be just shy of 90C

When you get home, check coolant temp with a meat thermometer (open cap slowly). Should be 87C or so. If coolant is too cool, then prob code is from t-stat not working properly. But much more likely sensor is bad.

The one I just replaced in our 2002 was a black one - apparently notorious for failing. Also for replacement buy from VW, apparently aftermarket ones also let out the ghost quite quickly.

Cheers.
Jeff

Thanks, unfortunatly i dont have the VCDS. I may just have to try the meat thermo method sometime. Could a bad sensor affect mpg? So far after i cleared the code it hasnt come back. Im definately thinking its a bad sensor. Will id parts have replacements?
__________________
2005 Jetta GLS TDI: Reflex Silver, Black Velour, 15%tint Front, 5% Back, Gator Tuned, Ventectomy, Magnaflow High flow Cat, Aero Turbine Muffler, AFE Cold Air Intake, Philips Xtreme Power Headlights, 215/60/15 Goodyear Eagle Gt's
LadiesMan217 is offline   Reply With Quote
Old August 13th, 2010, 18:11   #4
LadiesMan217
Veteran Member
 
LadiesMan217's Avatar
 
Join Date: Feb 2009
Location: Springfield, MO
TDI(s): 2005 GLS TDI
Fuel Economy: 33mpg city
Exclamation

Well so far the code hasnt come back but i just filled up today and its only 30 mpg. I havent been that low since winter. Should i just replace it? Is there a how to on here about it and where's the best/cheapest place to purchase one from? thanks guy
__________________
2005 Jetta GLS TDI: Reflex Silver, Black Velour, 15%tint Front, 5% Back, Gator Tuned, Ventectomy, Magnaflow High flow Cat, Aero Turbine Muffler, AFE Cold Air Intake, Philips Xtreme Power Headlights, 215/60/15 Goodyear Eagle Gt's
LadiesMan217 is offline   Reply With Quote
Old August 13th, 2010, 19:56   #5
TonyJetta
Veteran Member
 
Join Date: Sep 2005
Location: Tucson, Az
Fuel Economy: A5: 35mpg Avg / B4: 41mpg Avg
Default

Some preferred sources:
1stvwparts.com - Auburn Wa VW.
idparts.com
worldimpex.com
boraparts.com

Tony
__________________
Diesel fleet: 2006 Jetta, TDI, DSG, 35MPG avg; 2006 DC Cummins, CC/LB/DRW, Jake, 15.5MPG avg, 47kmiles; 1996 Passat TDI, 5sp, Project car! 204k miles, Avg 42mpg / best 48.9mpg, Troubleshooting Links: Whitedog's No Start Trusted TDI Mechanics A4 Limp Mode IP Timing Timing Belt FAQ A3/B4 Low Power Cyl Head Repair Fault Codes What you have just read is an opinion...take it as you see fit!
TonyJetta is offline   Reply With Quote
Old August 13th, 2010, 22:11   #6
LadiesMan217
Veteran Member
 
LadiesMan217's Avatar
 
Join Date: Feb 2009
Location: Springfield, MO
TDI(s): 2005 GLS TDI
Fuel Economy: 33mpg city
Default

Quote:
Originally Posted by TonyJetta View Post
Some preferred sources:
1stvwparts.com - Auburn Wa VW.
idparts.com
worldimpex.com
boraparts.com

Tony


Great, thanks. I found an old how-to by "tkindler" so i'll pick up the green sensor and take a crack at it. One question though, my temp gauge has always been stable, if the sensor was really bad wouldnt it be all over the place?
__________________
2005 Jetta GLS TDI: Reflex Silver, Black Velour, 15%tint Front, 5% Back, Gator Tuned, Ventectomy, Magnaflow High flow Cat, Aero Turbine Muffler, AFE Cold Air Intake, Philips Xtreme Power Headlights, 215/60/15 Goodyear Eagle Gt's

Last edited by LadiesMan217; August 13th, 2010 at 22:25.
LadiesMan217 is offline   Reply With Quote
Old August 14th, 2010, 06:34   #7
TonyJetta
Veteran Member
 
Join Date: Sep 2005
Location: Tucson, Az
Fuel Economy: A5: 35mpg Avg / B4: 41mpg Avg
Default

I'm pretty sure the '05 is like my '06, in that there are 2 temp sensors. I had a similar issue and had to replace the one near the thermostat.

Tony
__________________
Diesel fleet: 2006 Jetta, TDI, DSG, 35MPG avg; 2006 DC Cummins, CC/LB/DRW, Jake, 15.5MPG avg, 47kmiles; 1996 Passat TDI, 5sp, Project car! 204k miles, Avg 42mpg / best 48.9mpg, Troubleshooting Links: Whitedog's No Start Trusted TDI Mechanics A4 Limp Mode IP Timing Timing Belt FAQ A3/B4 Low Power Cyl Head Repair Fault Codes What you have just read is an opinion...take it as you see fit!
TonyJetta is offline   Reply With Quote
Old August 14th, 2010, 07:02   #8
LadiesMan217
Veteran Member
 
LadiesMan217's Avatar
 
Join Date: Feb 2009
Location: Springfield, MO
TDI(s): 2005 GLS TDI
Fuel Economy: 33mpg city
Default

Quote:
Originally Posted by TonyJetta View Post
I'm pretty sure the '05 is like my '06, in that there are 2 temp sensors. I had a similar issue and had to replace the one near the thermostat.

Tony

Mine is the a4 design from early 05, before the design change..
__________________
2005 Jetta GLS TDI: Reflex Silver, Black Velour, 15%tint Front, 5% Back, Gator Tuned, Ventectomy, Magnaflow High flow Cat, Aero Turbine Muffler, AFE Cold Air Intake, Philips Xtreme Power Headlights, 215/60/15 Goodyear Eagle Gt's
LadiesMan217 is offline   Reply With Quote
Old August 14th, 2010, 18:03   #9
TonyJetta
Veteran Member
 
Join Date: Sep 2005
Location: Tucson, Az
Fuel Economy: A5: 35mpg Avg / B4: 41mpg Avg
Default

Quote:
Originally Posted by LadiesMan217 View Post
Mine is the a4 design from early 05, before the design change..
If it's a PD, then it's likely similar...2 temps sensors. One at the back of the head, PITA to replace, and one at the lower radiator hose, where it goes into the thermostat, easy to replace. The one in the lower radiator hose is the one I had to replace.

Tony
__________________
Diesel fleet: 2006 Jetta, TDI, DSG, 35MPG avg; 2006 DC Cummins, CC/LB/DRW, Jake, 15.5MPG avg, 47kmiles; 1996 Passat TDI, 5sp, Project car! 204k miles, Avg 42mpg / best 48.9mpg, Troubleshooting Links: Whitedog's No Start Trusted TDI Mechanics A4 Limp Mode IP Timing Timing Belt FAQ A3/B4 Low Power Cyl Head Repair Fault Codes What you have just read is an opinion...take it as you see fit!
TonyJetta is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 11:48.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2014
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
1996 - 2013, All Rights Reserved
Page generated in 0.15569 seconds with 9 queries
[Output: 94.57 Kb. compressed to 80.92 Kb. by saving 13.65 Kb. (14.43%)]