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Lumpy rough from cold? 01039 - Coolant Temperature Sensor Idiots guide


Active Member
Oct 3, 2009
Shifnal, Shropshire
I know this subject has been covered before in parts but I have decided to put together a small guide to culminate all the info I have read up on this fault

Recently I’ve been getting rough tick over and hesitation when pulling away from cold so I decided to investigate with the help of vag com.

After running a fault scan vag com threw up the below fault code even though I didn’t get any management light.

With this code I searched the ross tech wiki site. The symptoms described matched what I have been getting wiki.ross-tech.com

Address 17     -------------------------------------------------------
   Controller: 1M0 920 922 FV 
   Coding: 05424
   Shop #: WSC 62010
   VSSZZZ1MZ3R139108     SEZ7Z0C2040358
1 Fault Found:
01039 - Coolant Temperature Sensor (G2)
            30-10 - Open or Short to B+ - Intermittent
With a little more searching I found the vag part numbers for the sensor, O ring seal and retaining clip

Coolant Temperature Sensor “green top sensor”: 059 919 501A

O Ring Seal: N903 168 02

Retaining Clip: 032121142

It turned out that CES in Telford where I got the parts from actually supplied the O ring with the sensor. I paid £15.57 for the sensor and 41p for the clip. I got the clip just as a back up in case I broke the old clip trying to get it off

I left my car over night to make sure the coolant was cold. Dont want boiling hot water all over me.

OK the here goes lets get grafting!! For all of 10 mins lol

Take the engine cover off to reveal all the engine gubbins (I aint got a clue what it all does either).

Ive marked with the red arrow where the sensor is located.

Another pic of the location of the sensor

Notice the horse shoe shaped clip that pinches the sensor into its housing via two slits in the housing. I got a flat blade screw driver and slowly levered the clip out. I didn’t break the clip after all so I didn’t need it, but for 41p its better to be safe than sorry

With the plug still on I gave the sensor a little twist and it popped out. It was easier to get the plug off it when out of its position. Remember the old O ring will be sitting in the sensor housing so just stick you little finger in to get it out

I reattached the plug rather than trying to do it when the new sensor was in place. The sensor goes in with the arched side towards the engine and flat side towards the airbox.

Now to fit the retaining clip. It slides in to the two slits on the sensor housing. I just pushed it on with my thumb.

Another pic of the new sensor

Now reattach the engine cover.

The old sensor with its clip

You’ll be glad to hear that all the hard back breaking manual labour is over.

All there is to do now is clear the fault code in block 17 “instruments” in vagcom and then your done.

Time for the Mrs to lay on the tea and biscuits for her hard grafting man

Address 17     -------------------------------------------------------
   Controller: 1M0 920 922 FV 
   Coding: 05424
   Shop #: WSC 62010
   VSSZZZ1MZ3R139108     SEZ7Z0C2040358
No fault code found.

Trust me, if I can do this job any idiot can and ive been told the stealers charge in the region of £150 for this work.

Andrewcupra TDI

Resident Desk Jockey
Apr 30, 2008
in the mountains ( Wales )
any ideas if this is same part for the arl diesel engine , i have the exact same problem , i have changed one sensor and that was the fuel temp sensor which made no difference

i dont seem to be getting any fault codes either



Active Member
Oct 28, 2006
Yea, i just spent half an hour looking, no luck what so ever.
So thought id come in and have a cuppa and hope for someones knowledge on here :D


This is probably a bit late by now, but I have just done this job on my ARL (TDI 150)...

The sensor on the TDIs all seem to be located in a much more awkward position than the petrol engines' - it is round the back of the cylinder head on the right hand side, if you are standing in front of the engine bay.

Feel round the back just above where the gearbox mates with the engine and you will feel it with the connector and wire sticking out towards the bulkhead.

The proceedure for the TDIs is not as easy as the petrols and my hands (and engine and gearbox) got covered in coolant while I was trying to do it.

I got the sensor which came with a new O ring but kept the old plastic clip as it seemed fine.

- Coolant will gush out the back of the hole once the sensor is removed, so get lots of towels and some spare G12 coolant (I used Halfords G12 spec stuff).

- Once you remove the plug try and cover it with something (I used the finger from a latex glove!) to stop coolant accidentaly splashing on the pins.

- Unclip what you can to get better access. If you can get both hands to the area it will help alot.

- Use a screwdriver or similar to pry the retaining clip downwards using the gap in the clip. Be very careful when doing this as I very nearly lost it into the engine bay!

- Put a tiny smear of waterproof grease (I used silicone) on the new O ring fitted to the new senor ready to help ease it in.

- Pull out the old sensor out with the new one ready to go immediatly back in, coolant will start gushing as soon as the old one is removed. Oh, and make absolutely sure the old O ring comes out with the old sensor!!!

- Once the new sensor is fitted snugly, slide the retaining clip back into it's groove from beneath. Ensure it has slid all the way up correctly and the end of the sensor is straight ( first time i did it one side missed the groove and the sensor was slightly wonky).

- Plug the connector back in and top the coolant back up - Job done! (on my 150 the code cleared itself).



I've got an 03 tdi sport 130 and my coolant light beeps and flashed every single time i turn the engine on.

A friend of mine had the VAG Diagnostics kit and it came up with exactly the same faults as shown above. I've replaced the coolant sensor, i was given a green one but it was a 4 pin so i had to go to volkswagn and get a 2 pin which is black (if that makes any difference).

He's cleared the fault using the vag and rerun the diagnostics and it came up with no faults. but when I've started the car after this the warning light has come on again.

Is there anything else i can do? the temperature is absolutely fine, it rises to 90c and stays there solidly

Thanks in advance
Listers, parts supplier