P0128 Code

MORTAMIR

Veteran Member
Joined
Jun 2, 2020
Location
Washington
TDI
MKIV GOLF 05 BEW, DURAMAX LBZ, X5 35D
So i been getting this code more often recently. Before it would come and go. Now it is summer and i wouldn't think i would have a problem with my coolant temp being low but my ECU keeps showing this code. I don't have a VCDS. I just use Torque to scan when i see my almighty engine light come on.
So the help i need from you all would be, Starting with the least cost first, what would be elimination process to get this code sorted out?

I have a 05 BEW M5 with 207k. EGR valve and cooler delete, new turbo, new (to me) BRM intake manifold, new 3inch exhuast turbo back, new map Sensor, New tune all within the last 30 days.

EDIT: I also replaced the large fan recently.


Could this be a problem with my new tune?

I dont have a garage or many tools either and my wife has been laid off from work so we are a bit down right now.

I have read through a couple of discussions about this.
https://forums.tdiclub.com/showthread.php?t=359453 Seem like a place to start for no cost.




Just to confirm this is one the thermostats i would need to replace?
What is the other one?
 
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SteverTDI2005

New member
Joined
Oct 24, 2019
Location
Champaign, illinois
TDI
2005 Beetle TDI
I had a 1999 Beetle. Had same code. The little blue Thermometer Icon showed up on dash. I replaced Coolant Temperature sensor (059919501A Coolant Temperature Sensor for Volkswagen for Audi with O-Ring and Clip 158-0629) Bought on Amazon it fixed the problem. 6$ I think I only needed a flat screw driver(to pry retaining clip out)

I have read it could also be the Thermostat. It was not the problem in my case.
Ironically I have the same problem now on my 2005 TDI.
I have read black ones are usually original. And the green ones are new and more likely to be better quality. YMMV

I am not able to find the location of this sensor.
If you decided to do this post a pict..
 

MORTAMIR

Veteran Member
Joined
Jun 2, 2020
Location
Washington
TDI
MKIV GOLF 05 BEW, DURAMAX LBZ, X5 35D
Replacing the thermostat this weekend. I will let you know if it resolves it.
 

Herm TDI

Vendor
Joined
Nov 21, 2001
Location
Richmond, Maine...The far side of Witsend
TDI
2002 Golf GLS Malone Stage 3, P+520 nozzles, 11MM Inj pump, Sachs VR6 clutch, Stelth Race Pipe, Immo Deleat, EGR Deleat
1. Verify that you're using VW / Pentosin "Pentofrost" coolant @ 50% mixture
2. Thermostat has become weak and is not full closing.
3. Eng. Temp sensor ( 059-919-501-A) is failing.
 

afterthisnap

Veteran Member
Joined
Jul 24, 2012
Location
Mountain West
TDI
Jetta wagons, ALH/CJAA
Malone stage 3? I'm getting the same code after the tune but I haven't put many miles on it recently to chase it down.
 
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gforce1108

Top Post Dawg
Joined
Aug 2, 2006
Location
Newburgh, NY
TDI
04 Jetta GLS BEW, 14 Audi A7 V6 TDI, 13 Porsche Cayenne V6 TDI
I have 2 BEWs that also intermittently throw that same code and only in warmer weather. On mine I've replaced the thermostat (aftermarket I think) with no improvement. I just ordered an OEM thermostat for the other car to test.

I see Malone and others can address this in their tune listing that the BEWs are ultra sensitive to coolant temp. I know that on mine - it usually happens around 130 degrees as the car is warming up. Mine is a bit slow to do so with the EGR cooler deleted. The other car is bone stock.
 

afterthisnap

Veteran Member
Joined
Jul 24, 2012
Location
Mountain West
TDI
Jetta wagons, ALH/CJAA
I poked around today and saw a wet spot on top of the tranny. It looks like coolant is leaking from somewhere around where the coolant hose/temp sensor seals to the head. I'll bother with it some more tomorrow, but I'm going to bet the connector to the temp sensor is gnarly.
 

WolfgangVW

Veteran Member
Joined
Oct 16, 2011
Location
Alberta, Canada
TDI
2003 Jetta TDI - Manual
OP I believe I had this code years ago, same time in the summer more or less. I replaced the CTS and the code went away. However the following winter I had to replace the thermostat as it wasn't heating up. If I had to do it over I would have drained coolant and replaced CTS and T-Stat at the same time for the cost of the parts.

As well make sure you get the right T-Stat. The original one for the ALH anyway has kind of a double spring type setup. I was sold the gas one that doesn't have the double spring first off. Was a royal pain pulling mine out on a Saturday and not having the right part to put back in. As well I remember there is some sort of plastic flange / holder the T-stat sits in and there are some plastic tabs that like to break, which I also found out lol. I was able to get mine back in but I think the plastic piece is quite cheap and would have made reinstallation 10x easier after the tab broke. Not to say you will break yours.

This is all on my ALH and I see you have a BEW but it might be similar. Sorry I can't be more specific but this was probably 7+ years ago. Good luck!
 

WolfgangVW

Veteran Member
Joined
Oct 16, 2011
Location
Alberta, Canada
TDI
2003 Jetta TDI - Manual
I poked around today and saw a wet spot on top of the tranny. It looks like coolant is leaking from somewhere around where the coolant hose/temp sensor seals to the head. I'll bother with it some more tomorrow, but I'm going to bet the connector to the temp sensor is gnarly.
When I changed my CTS I read or was warned that sometimes the old O-ring remains in place and then you can accidentally install the new one as well with your new CTS, causing problems. Not sure if this helps but just a heads up....
 
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