OK, here goes......

I have a 2005 1.9tdi PD 8 valve. BKC build, manual 5 speed gearbox. I bought this car in 2008 and now have completed 292,000 miles.

So the engine management light came on reporting a G62 coolant temperature sensor problem. I have replaced both of the coolant temp sensors.  There is one at the bottom of the radiator on the passenger side and one at the side of the cylinder head above the transmission.

From what I can gather the sensor that relates to the G62 error is the one at the side of the head. I have replaced this now twice, the second time with an oem quality sensor just in case I had a faulty new sensor.

 

The problem I have is that the G62 error will not go away and the EML comes on usually when I start the engine but not every time. The car is running absolutely fine at the proper temperature but the cooling fans come on when I start the engine and I think they remain on nearly all the time. The tick over is very slightly raised when cold but does eventually go down to normal. The temperature gauge hardly works at all. If I drive for a long journey the temp gauge might work slightly but never gets to normal and usually goes back to zero. Usually, after a reasonable journey when i park the cooling fans are both still on but not always. I did take it to a recommended person and he connected his whiz bang computer and the car just reports the G62 coolant error. It also reported that the temperature was -39 degrees so it appears that the ecu is not getting the info from the sensor. I do not have access to anything other than a very cheap chinesium code reader that I use to turn off the EML but it always inevitably comes back again, usually when I start up in the mornings but not always. All the time it tells me there is a coolant temp sensor error. The temperatur gauge on a day to day basis is not operating but, as i say it will suddenly work after a fashion and then either stay working or drop back down to zero but never reaches normal. (The thermostat is definitely working properly and is high quality).

 

Both of the sensors are of the two wire type.

 

My guess, and it is a shot in the dark is that there may be a short to ground, either permanent or not but I really just don't know what the problem is. It could be the ECU, I suppose (in which case the car will be sent to Skoda heaven) but everything else on the car is working very well considering the high mileage of the car.

 

If anyone has any diagnosis or knows someone near to North Herftordshire who knows about these things I would be very grateful for all advice and contact names. I am a pensioner so cannot afford to spend hundreds of pounds chasing a problem such as this one with no guaranteed diagnosisor success..... If you are still reading then thanks and well done!

 

I will watch out for all replies, so thanks everyone

Tom

Edited 21 January, 20251 yr by ThomasP

Open circuit (broken or very badly connected wire)  is consistent with a falsely low temperature reading, not a short circuit.

Most likely breakage point would be just outside the cable entry of the connector, so ought to be obvious.

 

What occasionally happens instead is that the metal encasement of the sensor goes porous, and coolant gets into the innards of the sensor. You'd think that replacement would solve this, but unfortunately once it's inside the connector, it can corrode the connections of both sensor and loom connector contacts, and even wick its way along the wires, within the insulation jacket.

 

If you unplug the loom connector of G62, does it seem damp inside, and do the connector contacts look clean and shiny, or crusty and corroded?

Good light and magnification may be required to see.

Pete

Many thanks for the response........

 

The connector looks fine and shiny. In fact, if I start the engine with the connector not fitted to the sensor both cooling fans run and if I then connect the connector to the sensor the fans will stop but the error is still reported and the next time the fans will start when i start the engine.......so it might indicate the wiring (or at least the connector) is good but I need a competent person to look at it, I think...

but thx v m etc for your reply

Tom

This might sound stupid but it worked for me. Three times mine has been back to Skoda dealer each time saying "it could be anything so would require searching for problemn so bring it in for two days !. Anyway saw this on Utube and tried it and problemn solved. Disconnect both battery leads and connect then together.Wait for around twenty mins , then reconncet to battery. Could not believe it , problem solved.

Pastiche, thx v v much for the reply.

 

I'll give it a go and report back

Thanks again

Tom

Pastiche...........nah!

I did what you suggested but it's still the same.

Thanks very much for the suggestion though

 

Regards

Tom

On 22/01/2025 at 02:56, ThomasP said:

The temperature gauge hardly works at all. If I drive for a long journey the temp gauge might work slightly but never gets to normal and usually goes back to zero.

Is the engine actually getting warm?

 

Hop out and feel it. Should be too hot to hold hand in head or engine block.

 

You say the guage doesn't work, but it may be reading correctly but the engine is so cold (from fans running constantly) that it never reads above its low mark.

 

Maybe a thermostat problem on the fan side. Can you unplug then fans and drive with them unplugged?

 

What happens then?

 

Maybe the coolant error is due to the system thinking the coolant is empty because its not reading a high enough temp.

1 hour ago, BlueWagon said:

Maybe the coolant error is due to the system thinking the coolant is empty because its not reading a high enough temp.

 

🤣🤣🤣

 

Yeah why take any notice of the coolant level sensor!

 

No coolant = high temperature.

BlueWagon

Thanks very very much for the excellent response and suggestion.

 

The engine is definitely running at the correct remperature, these were my thoughts at the beginning of this problem....

I need to get it looked at by a proper auto electrician who knows VWs, Skodas etc.

Practically speaking, the car isn't worth that much any more, I don't have hundreds of pounds to chase a problem I might never solve.

 

When this neverending freezing cold snap finally relents I might try and chase this broken wire business myself but I am not too confident with these things(everyone keeps telling me that a broken wire is most probable) and it definitely does fit the symptoms. Apparently, a favourite place for a broken wire is under the batterry where the loom runs close to the body... but who knows.

 

 

Annoyingly, the other day the temp gauge burst into life again afetr a long period of only moving a couple of mm for the last few weeks but again, it did not go to read normal and dropped down to very nearly cold.

 

At nearly 300,000 miles the problem could be anything but I don't think it's the ecu (just my feeling).

 

If there is a knowledgeable auto electrician reading this please get in touch. I am in the North Hertforshire area...

 

Thanks again blue wagon  and anyone who has read this

 

Tom

22 hours ago, J.R. said:

No coolant = high temperature.

 No coolant = temp sensor doesn't read a high temp cause it's not sitting in hot water. 

 

If the temp guage isn't working but the engine definately gets up to temp, Id think your issue is very much related to the guage and the wiring and the plugs into ECU may be the fault.

 

The car simply can't read its temp so runs fans to make sure it's not overheating.

Blue Wagon

 

Thanks again.........this exactly what I think. The engine is 100% running at the correct temperature. I think the wiring is the issue and this is why I think I need an experienced person to look at it . As I say, when the awful weather improves I will have a look myself but of course I shouldn't think a proper auto electrician would "like me to help" bt disturbing everything.

 

Once again, I thank you for helping.

 

I'm trying to find a recommended loacal auto electrician but I just don't know anyone

 

 

Thanks again

 

 

Tom

5 hours ago, BlueWagon said:

No coolant = temp sensor doesn't read a high temp cause it's not sitting in hot water. 

 

In your theoretical but not in my practical experience world.

 

5 hours ago, BlueWagon said:

The car simply can't read its temp so runs fans to make sure it's not overheating.

 

Once again a theory being recounted as fact, how do you square your theory of no coolant so fans running to cool a radiator containing no coolant?

 

As I stated before the vehicle has a coolant level sensor, if the coolant level is low it switches on the warning light.

18 hours ago, J.R. said:

your theoretical but not in my practical experience world.

 

I've personally seen it happen on Toyota Landcruisers and a few other makes too.  The temp guage read lower than normal after a momentary overheat. Upon stopping we found the coolant was no longer occupying the top half of the engine. Guage read slightly lower than normal. Motor was roasting hot.

 

Also on a Mazda one time after they hit a roo and punctured the radiator. They continued to drive (as temp guage was reading low) with no coolant.  They quickly had an overheating condition which led to a smoked engine. All this time, no indication of over temp on the guage.

 

So yeah, the theory does play out in practice.

18 hours ago, J.R. said:

you square your theory of no coolant so fans running to cool a radiator containing no coolant?

There is no temp signal (for whatever reason). So on order to ensure the best chance of NOT overheating, the ECU commands the fans to run. Better to run cold than overheat. 

Seems like a smart redundancy move to me.

 

Like when early ecus, and probably modern ones loose a valid knock sensor reading they retard ignition timing so much that pre-ignition is extremely unlikely.

 

Again, fail safe redundancy built in.

 

That's my take on why old mate's fans are running. 

You do like to invent things to suit your imagination.

 

The 3d mapping for ignition and fuelling is written to prevent pre-ignition under all conditions using the lowest octane rating fuel specified for the engine, the ECU not knowing what fuel has been put in the vehicle will advance the ignition timing beyond this until the piezo-electric knock sensor gives an output the spark timing is retarded to just beneath this point, this happens dynamically hundreds of times a second. It allows the maximum benefit to be gained from higher octane fuels.

 

I have owned a 2006 1.9TDi BKC engined car and it does not have what you attribute to it.

 

 

@ThomasP, if you would like the wiring information about which engine ECU pins the G62 sensor connects from, please share your VIN by private message so I can look up for you.  May be useful to an autospark, if not yourself.

Everyone

Thanks for all the replies

 

Tom

Update - Now solved

Firstly, thanks to all the people who offered advice/help.

The problem has indeed turned out to be a wiring problem which was resolved by completely disconnecting the original wiring in the loom and replacing both cables direct from the sensor to the ECU as per wiring diagram.

Once this was done the car immediately reverted to correct behaviour.

The added, very pleasing wrinkle is that a parasitic drain that the car has suffered from for years now seems to have disappeared also.

Hoorah!!

So, thx again everyone......Until the next time

Regards

Tom

Hi Tom, could you please message me? I have a 2007 Skoda Octavia 2.0 TDI with very similar temp sensor error and error code. Probably wiring. Would like to have some more info regarding your fix and how you did it.

@ThomasP will be more likely to see your request now that I've tagged him but, @svims best if you let me know the VIN for your car. That will allow me to look up the coolant temperature sensor wiring info that's most appropriate, which is not necessarily the same as on Tom's car.

On 12/05/2025 at 11:38, Breezy_Pete said:

@ThomasP will be more likely to see your request now that I've tagged him but, @svims best if you let me know the VIN for your car. That will allow me to look up the coolant temperature sensor wiring info that's most appropriate, which is not necessarily the same as on Tom's car.

Struggeling with the same problem at the moment. BMN, 200000 miles.

Replaced the G62 twice. 1x Hella, 1xFebi.

VCDS always showing 90 degrees coolant temperature, fan running. Also showing the 90 degrees with G62 disconnected.

Error Message alwas the same (000280 sensor for coolant temperature G62 - P0118 - 006 signal to high).

I also think there is wiring problem :-(

As i`m new to this forum (I'm German), i'm not able yet to send PM @Breezy_Pete to submit my FIN for a wiring diagramm for my BMN.

Best regards

Thom

Edited 3 August, 20253 Aug by Samoht26

by the way: is the a G83 sensor in the BMN or only the G62?

Samoht26

Hi there

I am not the world expert in any way regarding this problem I had with my car. Breezy Pete was a big help to me and after much thinking and theorising on my problem I came to the conclusion that it was indeed the wiring. When I connected up my very, very cheap obd2 reader it showed the temperature at -39 degrees which was obviously not correct. Both the fans would start about 10 seconds after turning the ignition on and the tick over was slightly raised and the car never felt as though it was running "easy". Also, the temp gauge was very unpredictable in that it mostly didn't work at all but would occasionally make it way towards normal but never get there and then eventually fail again. The fans remained on all the time I was using the car. However the car was obviously running at the correct temperature.

If your G62 temp sensor is the two wire type the the circuit for it is simple. The two wires come straight from (via the wiring loom) to the coolant sensor and the straight back again with no junctions or connections involved in the wiring.

With the fantastic help of a local mechanic we actually made the repair together by cutting both of the wires near to the sensor, identifying the other end of the two wires at the ECU, cutting those near the plug and simply replacing the wiring. We never identified EXACTLY where the wiring fault was but the theory was that one or both of them had shorted to earth and/or to each other

This instantly cured the problem and as I type this message the car has behaved perfectly ever since so for me this was a definite fix.

I hope this helps you

Good luck

Regards

Tom

@Samoht26 on your car there is a G83 as well as G62. G83 is described as Coolant temperature sender at radiator outlet, so I guess it is near the bottom hose connection to the radiator.

Wiring to each is as follows:

G62 pin 1 red/grey wire to engine ECU pin 52 of the 60-way connector

G62 pin 2 brown/grey wire to engine ECU pin 53 of the 60-way connector

G83 pin 1 yellow wire to engine ECU pin 37 of the 60-way connector

G83 pin 2 brown wire to engine ECU pin 38 of the 60-way connector

Is there any sign of wetness inside the loom plug for G62?

Let me know if a pin diagram of engine ECU connectors is useful, although they are usually marked on the mating face, I think.

6 minutes ago, Breezy_Pete said:

Is there any sign of wetness inside the loom plug for G62?

Thanks a lot Pete!!

Yes, I noticed that the loom plug was a little bit wet. But maybe it got wet while disassembling, because I dismounted the sensor from the pipe with the plug still mounted on the sensor.....