Vag-Com error: Fuel Temp Sensor

Ok... I ust got my Vag-Com and got an Engine error

00539 - Fuel Temperature Sensor (G81)
30-00 - Open or short to B+

I have read all the posts about the FTS but mine is different!
My Vag-Com mesurments show that the FTS is locked at -5.6degC.

So basically my car is running lean due to the fuel density mapping the ECU is doing when pumping fuel - cold fuel is denser so the ECU will inject less fuel to get the same result if fuel is a different temp.

So Is it bad to keep running like this?
Mind you - the last time my car was Vag-Com'd was when I had the Timing Belt replaced and that was 2 years ago. So I could have been rinning lilke this since then!

Car is not affected. No stuttering, no lumpy idle.... it runs perfectly like the day I got it 6 years ago (too a degree)

Replacing the FTS would mean that my car would run better!
As every one else who FTS died reported the FTS was locked in at high temps like 100degC - which meant that the ECU was pumping more fuel than should be and more smoke produced in theory.

I know I have to replace it to get the TDi timing to work etc as these require FTS to be withing operating range - which it is not at the moment.

The ECU will "plug in" a different fuel temp value if it sees the current sensor is sending a corrupt value. That's why the car continues to run normally. And that is also why it set the DTC. So you will not harm anything. And remember that a diesel is a variable ratio engine, so the terms "lean" and "rich" do not apply.

Luckily these little sensors are cheap, and if you can find the part number you can have the dealer order you one (they likely will have no idea what you are after, but rest assured they can get one) and you can take the top of the pump off and replace it yourself.

Lots of dealers replace the whole injection pump instead for this one silly little sensor. That is why I have run accross quite a few folks driving around for a couple years with the DTC set...because the dealer told them they needed a $2000 injection pump! But no harm had been done, car runs fine.

Have you modified your car in any way? Specifially, have you put a tuning box on the car? It is a performance box which hooks up to the fuel pump. This could cause readings to go funny. Otherwise, replace the FTS, and that should solve your issue.

I'm thinkg about getting PP520's and maybe later a Upsolute chip... but currently my TDi is stock to the bone... no tuning box.

I just have to wait for a call back from a guy I know if he can get the FTS in Australia otherwise I'm off to an US online store.

It is weird that my ECU put a value in of -5.6degC and not something like the other peoples +100degC - these people reported eratic stuttering and other little issues.

BTW: FTS's are all the same right? There should be no difference in which country I get the FTS?

It is weird that my ECU put a value in of -5.6degC and not something like the other peoples +100degC

Click to expand...

I have a similar problem in my Mk4, but it doesn't go away with a new sensor.
Did you resolved yours??

Yep... Got a new sensor $35 AUD posted. Local Shop had to order it from Germany.

Fixed my problmes and then some!

Sound my Fuel Pump to be a bit dirty:


Cleaned pump up some what better with just an old clean toothbrush.

Fired it up and with 10 seconds I could hear the difference - 10 sec for air to be pumped out of pump.

I could feel the engine is smoother. Idle is smoother.
I cleared the codes with Vag-Com and the fault code did not come back. Fuel temps were working properly and the Vag-Com TDi-Timing was also working. With the fuel at correct temps the TDi-Timing was perfect.

Took the car for a test drive and oooh what a feeling... car has so much power back.

Engine Shut down is also smoother... does not cluck as much as before.

I think it has made a huge difference.
I've been driving with a faulty fuel sensor for soooo long that I thought my was was always like that!

I also got my PP520's... just need to install them now.

Ok, thank you for the reply
Paul

Yep... Got a new sensor $35 AUD posted. Local Shop had to order it from Germany.

Fixed my problmes and then some!

Sound my Fuel Pump to be a bit dirty:

Cleaned pump up some what better with just an old clean toothbrush.

Fired it up and with 10 seconds I could hear the difference - 10 sec for air to be pumped out of pump.

I could feel the engine is smoother. Idle is smoother.
I cleared the codes with Vag-Com and the fault code did not come back. Fuel temps were working properly and the Vag-Com TDi-Timing was also working. With the fuel at correct temps the TDi-Timing was perfect.

Took the car for a test drive and oooh what a feeling... car has so much power back.

Engine Shut down is also smoother... does not cluck as much as before.

I think it has made a huge difference.
I've been driving with a faulty fuel sensor for soooo long that I thought my was was always like that!

I also got my PP520's... just need to install them now.

Click to expand...

I realize this is an old post but do you have the Part Number from the Sensor and also what engine code is your engine? thanks

hello down under, which bit is the sensor in the photo?

Here are pictures of the sensor, VW and Bosch part numbers for the fuel/injection pump temperature sensor, and pump cover gasket.






If you want to keep your fuel pump looking stock, you will have to get this special socket to remove the one odd-ball bolt. You can order this socket from Metalnerd tools .



Most guys cut a slot in the head with a Dremel tool and use a screwdriver to remove the bolt. Then replace the old bolt with a regular torx bolt.

Those pictures/partnumbers made my day. I have had no luck with dealerships looking for those parts. thank you guys so much

good show

i Got Three (3)fuel temp sensors ordered they are coming from Wisconsin i guess. take about a week and half to get through my dealer. i will let everyone know once i have it installed. Why three? saves me having to do this all over again and i can always sell the third for dirt cheap/

Damn... You are looking at my rusty fuel Pump... LOL

My Engine is a 1Z Euro Spec

Yep that is the Sensor... from memory there is only one way it can go in as the screws are recessed into the sensor.

Just remeber that about 100 ml of diesel will spill out of the fump when you crack it open so protect your rubber hoses by using paper towel or rags around the pump before cracking it open to catch any spilt fuel.

There was also talk earlier or in another thread that you don't really have to replace the gasket... I did not and I still have no leaks - Oh and get the Triangle socket from MetalNerd (and the fuel filter line spanner at the same time for when you do your A3 Nozzle swap)

I don't understand how your car is still running!
With all that rust in the pump, how is it that the pump & injectors aren't clogged up? I don't know the construction of the pump but seeing as there is fuel at the top can't a particle of rust fall off and get pumped to the injector? And we all know how small the orifice is on an injector!
And lastly, I'd expect Bosche to use parts made of stainless steel to prevent that from happening!
Any thoughts?

DanEboy said:

I don't understand how your car is still running! With all that rust in the pump, how is it that the pump & injectors aren't clogged up? I don't know the construction of the pump but seeing as there is fuel at the top can't a particle of rust fall off and get pumped to the injector? And we all know how small the orifice is on an injector! And lastly, I'd expect Bosch to use parts made of stainless steel to prevent that from happening! Any thoughts?

Click to expand...

I've seen pictures of pump internals that were in worse shape, but I agree something very wrong is going on there. This looks like water contamination. As for the materials Bosch uses, these pumps are known to go half million miles easily if one uses clean fuel and changes fuel filters regularly.

Here is a pic of my pump from when I had to change out a failing fuel temp sensor. This pump had 305,000 miles on it at the time. I use additives regularly and generic #D2, usually BP. Stock VW fuel filters were used for the first 150,000 miles. Then I switched to the the Cat filter set up. The pump looks brand new inside.

Use Rust-o-Lom to remove rust. Alway put fuel conditioner that dispenses water from diesel in tank when filling. Rust develops when there is moisture. In diesels, the fuel in the tank gets warmed due to return of excess warm fuel from injectors. The warm diesel warms the air above it. When outside air cools the tank, the warm air in the tank gets cooled and in that process, water drops forms that fell in the diesel.

Where in the VAG-COM do you read what the FTS is reading?

I don't know the block number, but all the versions of VCDS I've used, have label files. It usually takes me a minute or 2 to see which block is right.

Tony

oilhammer said:

...Lots of dealers replace the whole injection pump instead for this one silly little sensor....

Click to expand...

Do you think a bad Fuel Temp Sensor could be why my 2011 CR140 (USA version) is suddenly having a hard time starting up after the engine is at operating temperature? She starts fine when cold and runs great all the time. The FTS (G81) is the first thing I wondered about. Thanks.

i think this specific sensor only applies to 1996-2003 cars with rotary pumps.

your common rail engine is a totally fuel different system in pretty much every aspect.

sorry it cannot be that simple for you...

try searching the jetta MK-VI section.

Ended up being loose electrical connection on the fuel pump. No issues since.

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