[LoneRider]

Hi BHPians,

This is my first post in team bhp and looking forward to some expert advice from you guys.
I own a Skoda Laura Elegance 2011 2.0 Tdi Automatic and have started facing some issues with my car as below:-
-When I turn the ignition to "ON" (car not started) position, the check engine and high coolant temperature signs get lit in the instrument cluster and the temperature Guage in the instrument cluster jumps to high and car starts making beep noise, sumiltaneously, the radiator fans start running with full speed (car is still not started with just the ignition to "ON" position)

-the car however manages to start after 3-4 cranks, the moment the car starts, the temperature gauge drops to "C" and stays there forever no matter how long I drive the car. And the radiator fans continue to run at full speed constantly.

-when I stop the car, the fans continue to run for about 10 minutes after the key is removed and then they stop.

-the car then starts without hesitation till the engine is hot. However, once the engine becomes cold, the entire process repeats again.

Additional information:- First I thought it is an issue with the instrument cluster since it had gone blank all of a sudden while driving. However, it came back up in seconds with the temperature gauge stuck to "C" and fuel Guage stuck at "Full" (it was a tank full of diesel in there). I drive for about 160 kilometers and noticed the fuel gauge still sitting at "Full". I removed the negative terminal of the batter to reset the ECU. The fuel gauge was back to normal, however, the check engine light and temperature warning light remained as it was. I got my instrument cluster checked and is all fine.

Showed it to a mechanic and he says ECM is faulty and needs to be replaced . I am not convinced here since a faulty ECM would not let the car start at all. The mechanic is just trying to fill his pockets real deep.

After a bit of browsing, I am suspecting the engine coolant temperature sensor to be the culprit and planning to get that replaced.

Please can you experts give your views as to what could be wrong as I don't want the mechanics to unnecessarily dupe me for a simple work and charge me a heavy amount.

One more help please, would anyone know how many sensors are present is Skoda Laura for engine temperature and where they sit under the hood?

[Y@SH]

Hi,

Get it checked at Select Auto, (Select Auto Garage - Sunil Shanbhag (Dadar, Mumbai)) Dadar by Sunil, I had an ECU issue on my 2012 skoda laura too. Car would not start sometimes and sometimes it would magically start.

No one was ready to repair it, others said the value of the car is lesser than cost of a preowned ECU! Got it checked by Sunil and he got it repaired for about Rs 25,000.

Give him a call and give my reference. Let me know if you need any help.

[scorpian]

Looks like a electric malfunction.Some wires may have shorted giving all false data to ecm.
You will need a good mechanic and it requires patience and tracing of all wires associated with the cooling circuit.
Hopefully your problem will be sorted out. Incase you can lay your hands on a used ecm then you can test it out just to be sure.

[pta320]

Please try to get an OBD scan of the car (costs 300-500 rs) from any nearby FNG (make sure they are using a high quality OBD scanner from Launch etc.) and let me know what fault codes if any are there. Also the OBD device can pull up the live data so check the coolant temperature also and let me know. Also take a snapshot of every live data while driving and while idling.

Without the fault code and actual live data, it's difficult to pin point what's wrong. It could be a bunch of issues like bad thermostat, bad coolant temp sensor, bad connection, and the worst of all bad ECM.

Usually the fan cuts in when coolant temperature reaches above 97 degree celsius. However, it's unlikely for that to happen on starting car for the first time which points that temperature readings are bad. But that's a very basic explanation, the real problem will be diagnosed only after an OBD scan. Also OBD scanners (good ones from Launch) are able to factory reset the ECU, so also do that. Also test the car with a different battery in case yours is going weak. If ECU isn't getting proper voltage, then also such issues can come up.

[LoneRider]

Originally Posted by Y@SH

Hi,

Get it checked at Select Auto, (Select Auto Garage - Sunil Shanbhag (Dadar, Mumbai)) Dadar by Sunil, I had an ECU issue on my 2012 skoda laura too. Car would not start sometimes and sometimes it would magically start.

No one was ready to repair it, others said the value of the car is lesser than cost of a preowned ECU! Got it checked by Sunil and he got it repaired for about Rs 25,000.

Give him a call and give my reference. Let me know if you need any help.

Hi Yash. I did ask one of my very old mechanic ( Nelson, near guru nanak petrol pump, Chakala, Andheri East) about ecu repair and replacement(used) cost. He has quoted me 8 thousand for repairs and approximately 20 thousand if repairs don't work and needs a replacement.

I don't want to directly go for the ECM as I suspect the coolant temperature sensor to be bad. However, as per you guys' suggestion, I will get the car scanned and try to get the complete error codes.

Will update once there is some progress..

[vishy76]

I might be the bearer of bad news here, but it does seem to be the ECM. I have noticed this happening in a Jetta TDI DSG too and a friend's Laura TDI, apart from a Passat B7 TDI on YouTube.

The problem arises when there is a short in the coolant circuit track on the ECM PCB, which causes the ECM to think the engine temp is always 150+ inspite of getting correct readings from the temperature sensor. The ECM has a fail safe mechanism where it will disable the starter and cut fuel off if the engine is overheating. Hence the car doesn't start. This is also the reason why the radiator fans keep running at full clip.

The ECM can be repaired in most cases though by a specialist for less than 10-12k. You can swap the coolant temp sensor with another car just to be sure it is the ECM, but I would definitely blame the ECM only.

https://m.youtube.com/watch?v=YS-ejw7nhnM&t=47s

P.S you can also see the location of the engine temperature sensor in the above video. As I said, swap it with a known good and see if it remedies the issue just to be doubly sure.

[Newtown]

Originally Posted by Y@SH

Hi,

Get it checked at.... select-auto-garage-sunil-shanbhag-dadar-mumbai.html......

I absolutely agree with this. Recently the BCM of my Civic was diagnosed as faulty. It was causing battery drain due to the doors locking and unlocking on their own. Had the BCM fixed and re-programmed by Sunil. Please do go to him.

[LoneRider]

Originally Posted by vishy76

I might be the bearer of bad news here, but it does seem to be the ECM. I have noticed this happening in a Jetta TDI DSG too and a friend's Laura TDI, apart from a Passat B7 TDI on YouTube.

The problem arises when there is a short in the coolant circuit track on the ECM PCB, which causes the ECM to think the engine temp is always 150+ inspite of getting correct readings from the temperature sensor. The ECM has a fail safe mechanism where it will disable the starter and cut fuel off if the engine is overheating. Hence the car doesn't start. This is also the reason why the radiator fans keep running at full clip.

The ECM can be repaired in most cases though by a specialist for less than 10-12k. You can swap the coolant temp sensor with another car just to be sure it is the ECM, but I would definitely blame the ECM only.

https://m.Youtube.com/watch?v=YS-ejw7nhnM&t=47s

P.S you can also see the location of the engine temperature sensor in the above video. As I said, swap it with a known good and see if it remedies the issue just to be doubly sure.

Hi Vishy76, thanks a million for the sharing the video. This is exactly what my car is doing. I will definately get the ECM checked but only after swapping the temperature sensor. Let me give it a try. I know an ECM repair guy and he has quoted me 8 thousand for repairs. Will reach out to him if the sensor swap does not work.

[LoneRider]

Originally Posted by LoneRider

Hi Vishy76, thanks a million for the sharing the video. This is exactly what my car is doing. I will definately get the ECM checked but only after swapping the temperature sensor. Let me give it a try. I know an ECM repair guy and he has quoted me 8 thousand for repairs. Will reach out to him if the sensor swap does not work.

Update: It was the ECM, got it fixed for 8 thousand and mechanic charges 1 thousand, total 9 thousand. Car is back to normal now. All the warning lights disappeared after I drove for about 1 kilometer. Thank you everyone, your views really helped a lot due to which I was able to pinpoint the issue without investing time in unnecessary diagnosis..

[Prash]

Originally Posted by LoneRider

Update: It was the ECM, got it fixed for 8 thousand and mechanic charges 1 thousand, total 9 thousand. Car is back to normal now. All the warning lights disappeared after I drove for about 1 kilometer. Thank you everyone, your views really helped a lot due to which I was able to pinpoint the issue without investing time in unnecessary diagnosis..

Hi, I am facing the ECM problem in my Passat. I am also from Mumbai. Can you please share details of where you got the ECM repaired and how was your experience.

I will be obliged if you could call me or drop me a whatsapp message and I shall get back to you. Have shared my contact number with you, kindly check your inbox please.

Thanks