1 hour ago, PipH said:

I think you will find the ECU is missing one of the several 12v supplies it needs.

 

You will need a wiring diagram to check.

 

VCDS will probably pinpoint the missing supply.

Thanks for your input! Do you happen to know where to find wiring diagrams? 

What is the engine code?

 

This may be relevant:

 

 

Edited 23 February, 20215 yr by MicMac

21 minutes ago, MicMac said:

What is the engine code?

 

This may be relevant:

 

 

BXE

And thanks for the tip! The fusebox looks flaweless, but I will check it. Relay 100 is working, tested it yesterday. But off course, corrosion can be a possibility. 

Update: mechanic diagnose it with VCDS. No errors came up and the car started like normal. Great! I tried to start it a few hours later.. Nothing, same symptoms as before. While I got towed, I tried to start it several times, and suddenly it starts. What the heck? When the car does not want to start, the ESP light, lights. Problem kinda sorted, but not really. Now I cant trust the car to start. 

And you cant really trust your mechanic either if he trots out the old line "it must be the ECU!" rather than say,"this one has got me puzzled, I need to look further, to try some other things" or "you really need to take it to someone more experienced in these matters than me".

True! Well. Now it did not start again.  Knocked on the ECU with a screw driver and then it started 

I take it all back

 

It would be worth removing the connector and cleaning the terminals but you will need an agle grinder and a lot of dexterity to remove the shear head fasteners and wiggle the ECU out of the security cage or to get the connector apart.

1 hour ago, J.R. said:

I take it all back

 

It would be worth removing the connector and cleaning the terminals but you will need an agle grinder and a lot of dexterity to remove the shear head fasteners and wiggle the ECU out of the security cage or to get the connector apart.

Hehe! I got the ECU out. The terminals and connectors look good. I will check the wires going into the connectors tomorrow in day light. Do you have any experience opening the ECU itself and clean it with alcohol? 

Yes, I bought and fitted a remapped "plug n play" ECU from Ebay, it looked like it had been opened so I removed the tamperproof fasteners to see if it had been resealed, it hadn't & was showing signs of corrosion, there were a few traces of the original sealant but large sections with nothing, I only had silicone to hand to bodge it with but at least it was then sealed.

 

Had it looked undisturbed I would have left well alone, the manufacturers sealing is usually excellent and you dont want to break that seal if you can avoid it, I learnt that from opening others through curiosity.

 

Its very well protected on the MQB platform cars, if the connector is good then there is nothing you can do inside other than cause additional problems, there are no connections to clean, its all flow soldered and covered with a conformal coating (think thats the right term).

 

They are incredibly robust, I had one from a burnt out Galaxy that was calcinated with a molten blob of fused plastic and copper wire strands where it had been cut from the loom, by carefull dissection and cutting with a fine blade I managed to seperate & remove the loom part of the connector by undoing the ejection screw, what was left looked like it had been deep fried & then put in a camp fire overnight but after fitting a new loom & rewiring the vehicle it started the engine & operated perfectly, a Ford dealer friend uploaded the latest software to it and ran full diagnostics & I drove for 100Kmiles & 4 years with it.

20 minutes ago, J.R. said:

Yes, I bought and fitted a remapped "plug n play" ECU from Ebay, it looked like it had been opened so I removed the tamperproof fasteners to see if it had been resealed, it hadn't & was showing signs of corrosion, there were a few traces of the original sealant but large sections with nothing, I only had silicone to hand to bodge it with but at least it was then sealed.

 

Had it looked undisturbed I would have left well alone, the manufacturers sealing is usually excellent and you dont want to break that seal if you can avoid it, I learnt that from opening others through curiosity.

 

Its very well protected on the MQB platform cars, if the connector is good then there is nothing you can do inside other than cause additional problems, there are no connections to clean, its all flow soldered and covered with a conformal coating (think thats the right term).

 

They are incredibly robust, I had one from a burnt out Galaxy that was calcinated with a molten blob of fused plastic and copper wire strands where it had been cut from the loom, by carefull dissection and cutting with a fine blade I managed to seperate & remove the loom part of the connector by undoing the ejection screw, what was left looked like it had been deep fried & then put in a camp fire overnight but after fitting a new loom & rewiring the vehicle it started the engine & operated perfectly, a Ford dealer friend uploaded the latest software to it and ran full diagnostics & I drove for 100Kmiles & 4 years with it.

Ok, I will leave it sealed I disconnected the ECU again and sprayed the connectors with electronic spray. It started right up after. Will leave it like this until tomorrow and see if it starts. It might be the wiring to the connectors. It is hard to see because they are stiff and bundled together, and I dont want to risk breaking the wires by moving them too much. 

Edited 1 March, 20215 yr by vegard

If you can heat the wiring with a hot air gun it will make handling old/cold/fragile wires easier to but may mask your original fault making it difficult to pinpoint.  I suggest you don't use this method in this instance.

 

I had a look on what data I have to hand and don't have ECU wiring for a BXE, presumably a BKC is the same but I cannot guarantee.

7 hours ago, MicMac said:

If you can heat the wiring with a hot air gun it will make handling old/cold/fragile wires easier to but may mask your original fault making it difficult to pinpoint.  I suggest you don't use this method in this instance.

 

I had a look on what data I have to hand and don't have ECU wiring for a BXE, presumably a BKC is the same but I cannot guarantee.

 

Thank you! If you have info on ecu wiring for BKC, I would appreciate it. It might be the same. 

Edited 2 March, 20215 yr by vegard

I have driven around, turned the car on and off for hours today. Starts every time. For now, I will conclude that it was bad wiring somewhere in the connectors going to the ECU. I soaked the connectors in electrical spray. Fingers crossed that it will run for a while now 🤞 

 

Thanks to all of you that have contributed 😃