coolant temp sensor help

Could someone please help, I have an 03 jetta wagen and I recall seeing a link with pictures on how to change the coolant temperture senor but I'm unable to find it .
I have a code PO 128 and I have read that this senor should be replaced

Thanks
03jetta

I think I found a link with some pictures they don't specify the year but I hope this helps others
http://www.inmud.co.uk/page28.htm

03jetta

sorry he does say it is for a TDI 115bhp engine

How about this picture:



The picture is deceving as it shows an impossible human view unless you took out the battery and air box and removed the coolant lines. The best hint in the picture are the 3 coolant heaters that stick up. Go to the right end of the cam cover and you will see the heaters. Stick your hand down behind and you will find it. Make sure the engine is cool and have a couple spare orings and spare clip as if you drop them you will never find them. Ask me how I know.

And where did you get that code from as the Factory Service manual doesn't show it as applicable for your car!

Curious Chris,

I used a Actron CP9125 and it gave me the code PO128, I first used it after my check engine light came on. I went to Advance Auto Parts and they used a more expensive verision . The code they got was a PO 671 (glow plug/heater cylinder) so he erased it , when the check engine light came back on, I bought the cheaper version (Actron CP9125), sure enough the same code (PO671) came up, so I bought a glow plug installed it after reading wingnut's glow plug article and haven't had that code come back.It does a nice job of reading codes, they give you a cd with all the codes listed, and a book with the codes .It also allows you to erase the codes which is nice so you don't have to keep going back to the parts store.
Hope this helps

03jetta

Oh I am more alert today and I found P0128 and the factory service manual says it is your coolant regulator, which I believe is tech speak for thermostat.

The thermostat is in the lower radiator hose that run back into the engine to the right of the oil filter housing and is pretty much under the injection pump. Obviously you are going to loose a lot of coolant so you might as well drain it. You take off the hose, then 2 bolts hold a connecting piece that supports the thermostat. Remove that turn thermostat 1/4 turn left and it will come out. Assembly is in the reverse direction, torque on the 2 bolts is 15Nm.

Curious Chris said:

Oh I am more alert today and I found P0128 and the factory service manual says it is your coolant regulator, which I believe is tech speak for thermostat.

The thermostat is in the lower radiator hose that run back into the engine to the right of the oil filter housing and is pretty much under the injection pump. Obviously you are going to loose a lot of coolant so you might as well drain it. You take off the hose, then 2 bolts hold a connecting piece that supports the thermostat. Remove that turn thermostat 1/4 turn left and it will come out. Assembly is in the reverse direction, torque on the 2 bolts is 15Nm.

Click to expand...

Of course it could be the G62 sensor but the only way to know for sure is to log the engine temperature using VagCom now known as VCDS.

Thanks Curious I might just replace them both

First time my temp sensor went bad I had a code for the G62. Next time, I got a code for the thermostat, but it was the temp sensor that was bad again.

I just had that same code and it was the thermostat

My temp gauge has been reading funny for a while. It reads properly and then it reads nothing. It reads anything in between too. I've suspected a bad CTS and for $14 it's a cheap-easy fix. I do get an engine code and got it read at my local Advance Auto. Turns out that it's #2 glow plug (I don't recall the code # right now).

My temp gauge has acted funny for about 3 months. The engine light came on only a month ago.

Is it safe to assume that these are unrelated? I actually expected that when the code was read it was going to tell me something about my temp sensor.

Another question: I have a 2003 Jetta, do I have the green sensor for sure? I can't really tell w/o taking it out.
In order to undo the electrical connection, does the sensor need to be out? or can it be unplugged and left clipped in?

thanks...
n8

"My temp gauge has been reading funny for a while. It reads properly and then it reads nothing."


I have had the same problem for 2 years but never got a CEL, so I never fixed it. Wonder if its the temp sensor as well? Just like I never fixed the weeping EGR or the drivers door lock sensor or the arm rest cover which fell apart a year ago, hazzy yellow headlight covers, and on and on and on.......... Some day I will fix em. Maybe i should just host a GTG to get moral support and motivation to do it.

Well, I haven't had a drivers door lock sensor issue yet. Not sure about a weeping EGR - I'll have to research that. What would I look for?
Arm rest latch - it's in my shopping cart on tdiparts right now.
Glow plug is in the cart too.

I'm thinking I'll just order the green CTS.

You know, I've never been to the northwest. That would be a fun road trip to get to your GTG. It would be what? 2000 miles? Up to 3 tanks to get there. 3 tanks back. Roughly $70 a fill so around $400 in fuel.

I'll bring the pads and rotors I haven't put on yet...

n8ronJ said:

My temp gauge has been reading funny for a while. It reads properly and then it reads nothing. It reads anything in between too. I've suspected a bad CTS and for $14 it's a cheap-easy fix. I do get an engine code and got it read at my local Advance Auto. Turns out that it's #2 glow plug (I don't recall the code # right now).

My temp gauge has acted funny for about 3 months. The engine light came on only a month ago.

Is it safe to assume that these are unrelated? I actually expected that when the code was read it was going to tell me something about my temp sensor.

Another question: I have a 2003 Jetta, do I have the green sensor for sure? I can't really tell w/o taking it out.
In order to undo the electrical connection, does the sensor need to be out? or can it be unplugged and left clipped in?

thanks...
n8

Click to expand...

You can unplug the sensor with the sensor still in the pipe. I did it yesterday on my A4 BEW. Ensure you feel for and push in the detent; don't just jerk.

Cleaning the plug and jack with Deoxit may help.

But at $14 you are correct. Just replace it.
It will not cause the glow plug failure, but it will cause the glow plugs to stay on longer than they should, or to not turn on when they should.

You will need some replacement coolant. Get the real stuff.
DanG

Is it normal for the CTS to read better when it's cooler out? Mine doesn't act up nearly as much now that it's not humid nor warm out.
Where do I get deoxit? Is it like a silicone lube? Squeeze tube?

Can I get the real coolant at a regular auto parts store? or just the stealer?

Deoxit from Radio Shack, or online. Spray cans one cleaner, one sealer, or something like that.

Coolant from a parts vendor here, (Bleachedbora, TDIPARTS, many others), and from the dealer. not regular autoparts store.

When you are dealing with electronics, ambient temperature can make a difference.

Dan