Returned from a long trip abroad : MCU won't boot and car won't charge D:

[nsxpert]

Hi everyone, I'm driving it in to the service center tomorrow with the little range I've got left, but wanted to know if there's anything I could do to resurrect my car in the meantime.

Was away for 4 months and left it plugged in and set the charge level to 50%. It's in a underground garage so I couldn't remotely connect to check on it while I was away unfortunately.
When I returned, doors, trunk, charge port, etc seem to work fine and the car will drive but the MCU is completely blank and no amount of rebooting seems to help. Charge level is closer to 15% right now.
There also seems to be no way to initiate a charge even though it will say 'ready to charge' on the instrument cluster after plugging in.

Any thoughts?

 

[boaterva]

Ugh. Since you can’t get to the menu, you can’t do what I’d suggest and power down and restart.

Assume you know the UMC actually has power?! And isn’t broken? Only time I’ve seen that (but it reported power issue) was with high wall voltage.

 

[nsxpert]

Ugh. Since you can’t get to the menu, you can’t do what I’d suggest and power down and restart.

Assume you know the UMC actually has power?! And isn’t broken? Only time I’ve seen that (but it reported power issue) was with high wall voltage.

The UMC seems to be fine and is lit up green like normal.... I drove to a nearby supercharger last night to try and get some range but it still wouldn't charge.

 

[boaterva]

The UMC seems to be fine and is lit up green like normal.... I drove to a nearby supercharger last night to try and get some range but it still wouldn't charge.

Good grief. Seems nuts that the MCU just died but could be something more basic if it won’t charge from two sources. Please let us know the diagnosis and result.

If a UMC and supercharger both won’t work, something is pretty messed up. Best of luck!

 

[Rocket58]

I’m having same problem. Large screen is dead and won’t reboot. I was driving and had ac on- no screen and app on phone won’t allow me to turn ac off

 

[Tam]

...Charge level is closer to 15% right now...

Something went wrong while you were away because a plugged-in Tesla should not have a 15% SOC. Somehow it just quit charging in your absence!

It might be a coincidence that the MCU just died while you were away.

 

[jdw]

I've had a similar thing happen, left the car plugged in charged to 65% and charging set to 50%. I left for 6 weeks and about 4 days into my trip the car drops offline, never to be seen again. When I returned, it was down to about 25% charge and took a long time, with multiple reboots, to get the MCU to power up. Once back, it was evident that it had tried to install software and failed, crashing the MCU.

The car didn't charge while I was gone because I had left timed charging selected which transfers responsibility for charging from the BMS to the MCU, which was no longer working.

Tip: Make sure you turn off timed charging before leaving for extended trips - that way, the charging is controllled by the BMS, not the MCU.

 

[Tam]

I've had a similar thing happen, left the car plugged in charged to 65% and charging set to 50%. I left for 6 weeks and about 4 days into my trip the car drops offline, never to be seen again. When I returned, it was down to about 25% charge and took a long time, with multiple reboots, to get the MCU to power up. Once back, it was evident that it had tried to install software and failed, crashing the MCU.

The car didn't charge while I was gone because I had left timed charging selected which transfers responsibility for charging from the BMS to the MCU, which was no longer working.

Tip: Make sure you turn off timed charging before leaving for extended trips - that way, the charging is controllled by the BMS, not the MCU.

Thanks for the info that took the mystery out of this scenario!

 

[jdw]

I would have thought Supercharging bypassed timed charging and that the BMS just remembered the charge % from the MCU setting, but on re-reading, it seems that it may not. It is possible that my "tip" would not have changed anything ... perhaps if the MCU charge % is unavailable, it's not going to charge by any means until the MCU is operating again.

 

[nsxpert]

Interesting.... I'll definitely change it to unscheduled next time, just in case.

Thanks!

I would have thought Supercharging bypassed timed charging and that the BMS just remembered the charge % from the MCU setting, but on re-reading, it seems that it may not. It is possible that my "tip" would not have changed anything ... perhaps if the MCU charge % is unavailable, it's not going to charge by any means until the MCU is operating again.

 

[J.J.]

If I leave my car plugged overnight and set the charge to 80%, I commonly find it at 77-78% in the morning. Is it supposed to continually keep the charge at 80% or just allow it to reach 80% and then all for vampire drain? Is there a threshold whereby the car realizes it's not charged to the selected percentile and reinitiate a charging cycle?

 

[jdw]

The car charges to 80% and then charging stops, so vampire drain will lower the charge from there overnight. Usually a 3% drop will trigger charging again.

Have you considered using timed charging so it finishes charging in the morning before you leave?

 

[Ken7]

In my case I require about an 8% drop from what I set before charging kicks in again.

 

[Joelgjr]

In my case I require about an 8% drop from what I set before charging kicks in again.

Same-ish for me