VIN729 - BSM: Contact power failure (ID:721)

[steve1an]

Dear Roadster owners, and Tesla enthusiastics,

I've recently encontered some problems with my roadster. It starts with a brick being unbalanced (3.76V min vs 3.97V max). So I decicded to have this brick rebalanced. After transport the vehicle over 1200 km from Shenzhen to Hangzhou, the vehicle could not start. VDS showing: "Battery cold, Can't start". I then check the ESS V&T, it shows one of the brick is -104 degree Celsius, which is clearly impossible, even though the environment temperature did drop about 10 degrees before and after the transport of the vehicle. After a few days, with weather getting warmer (~20 degrees Celsius), the vehicle did manage to start a few times.

The shop then dropped the ESS and taking out the sheet for balance, which took about 2 weeks. And then when they re-assemble the ESS, the vehicle could not start, it says another error: "BSM: Contactor power failure (ID:271)". They did check the BSM board and the power of the contactor seems fine.

So now we are trying to figure out if it is the issue of the contactor itself, or something wrong with the entire BSM board. Is it possible to buy the BSM assembly somewhere? Or does anyone one know the model (or equivalent model) name of the contactor? Or could it be some other problems that caused this error?

Many thanks,
Steve

 

[spaceballs]

Odd order of investigating.
Anyways for "it shows one of the brick is -104 degree Celsius," it's either the temp sensor in the sheet or BMB on that sheet.
Curious which shop is doing the work?

 

[louisyp]

I believe it also should be in the bmb or temp sensor. I have the battery cold error at my 2.5 roadster as well at minus 120 degrees at #3 and #4, however after talking the battery apart all temp resistors show around 12kohm so they seem ok measuring at the bmb connector. Anyone had this issue as well? Could this be a software issue at the bmb?

 

[spaceballs]

I believe it also should be in the bmb or temp sensor. I have the battery cold error at my 2.5 roadster as well at minus 120 degrees at #3 and #4, however after talking the battery apart all temp resistors show around 12kohm so they seem ok measuring at the bmb connector. Anyone had this issue as well? Could this be a software issue at the bmb?

Yep I've encountered bad BMB reporting bad temps. Though I was lazy and just used another BMB instead. I'm sure it would have been easy to fix though.

 

[louisyp]

Yep I've encountered bad BMB reporting bad temps. Thought I was lazy and just used another BMB instead. I'm sure it would have been easy to fix though.

I always understood you can not change a bad BMB since then BMB order - serial has changed. Or is this not right?

 

[spaceballs]

I always understood you can not change a bad BMB since then BMB order - serial has changed. Or is this not right?

There a few different ways, like IC swaps, programming, etc...

 

[louisyp]

There a few different ways, like IC swaps, programming, etc...

Many thanks for info, good to know. For now I will try to sort out the temp sensor issue at the bmb pcb, hope I can find the issue. So far all signals seem to be ok, as far as I can track down signals are measured at the bmb, no signs of broken components. Could it also be software related at the bmb? Would this be likely?

 

[spaceballs]

Many thanks for info, good to know. For now I will try to sort out the temp sensor issue at the bmb pcb, hope I can find the issue. So far all signals seem to be ok, as far as I can track down signals are measured at the bmb, no signs of broken components. Could it also be software related at the bmb? Would this be likely?

This might help, not 100% sure, just looking at my old notes, see if any ones are different than the others.
BMB connector Pins
4, (16 to gnd) Temp resistor 1, measue to Pin 15 on MCU.
6, (18 to gnd) Temp resistor 2, measue to Pin 22 on MCU.
8, (20 to gnd) Temp resistor 3, measue to Pin 20 on MCU.
9, (21 to gnd) Temp resistor 4, measue to Pin 19 on MCU.