I brought car for thermostat fault ( I did read it), so BMW dealer replaced thermostat, then after i got car back 1.5 day later again check engine light. I read a code it was same thing p0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature). Well after keeping car for almost a week they told me it's engine harness.

So I was thinking these mechanics are pulled connector while holding harness and torn harness a part.
Well this is not a case.

Well I had conversation with shop foreman, he had actually told me, that problem with V8 harness (sensor) is very common and reason is silicon is shorting pin on connectors. So soon or later all early V8 will have this problem, but the problem was address from 2010 and up.
So if you have thermostat code and you are already replace this, then next is harness (600 dollars just parts). I suggest to you read your store code see if you have at least ones a thermostat fault.

 

Yep, happened to me too, thank God I was still under CPO when it did - they had the car for 3 days to fix it

 

Could you provide information on harness information such as Part#, etc? You may find information in your service receipt.
I am also curious where it's located.

Thanks

 

I will do certainly right after I will get a car back. I will scan bill and post here.

I don't have car for 3 weeks already, because looks like harness is coming from Germany.

 

I could see if I still have it - it is the main engine wiring harness, the intake has to come off as it bascially goes to everything under the hood, as stated above this part is $600 plus.

 

Be careful with the need for a harness. The Stealer replaced mine, cost approx $689.00 for parts and $1,650.00 for labor covered by the exteneded warranty, and shortly after they replaced the harness the electrical problem came back, which was uneven idle where the tach jumped around,. Then the stealer said that my ECU needed to be replaced, which would have been another 2,000+ to replace. I took it to a different Stealer and they said there was nothing wrong with the ECU, my battery needed to be replaced, which is what I thought the problem was when I dropped the car off originally to the first stealer. So check your battery as a faulty battery seems to either throw off the diagnostic code showing fautly harness or ECU, or a harness is a great profit center for Stealers to screw warranty companies and owners. How do you really know the stealer replaced a harness?

 

Ok but you never had a thermostat problem?
I had check engine light for thermostat P0128.
Then after thermostat same code came back. Accordingly SB (don't remember a number), if same code came after already replaced thermostat, then harness. But the funny thing the car is still at dealer, and so right after they replaced harness the crankshaft sensor code, so they told on Friday they will keep a car for another couple days.

 

This happend to me as well. Luckily I was still under warranty and I got a E93 loaner for a day or two!

 

I had check engine light 3 times. First was an exhaust sensor issue. replaced under warranty, 3 weeks later check engine light, thermostat fault, replaced thermostat under warranty, 2 weeks later check engine light thermostat fault. They then replaced the engine harness... this was 3 years ago... not a fault since.

 

Got car back today after 3 weeks in shop. So they replaced harness, temp sensor on thermostat, crankshaft sensor, fuel tank ventilating well a lot things.