Bad headlight killed the whole vehicle?!?

[ajrettke]

So we've had some heavy rain for 2 days or so (DC Area). Never had any issues until yesterday morning when I tried to take my kids to school. From absolutely no errors, I got the screenshot below:

Obviously couldn't drive the vehicle so it got towed and this morning they fixed it. But it was simply replacing the headlight. Are our cars so vulnerable to basic errors they completely shut down? The technician note simply said the concerns were validated and the headlight replaced which was bringing down the system.

It seems to me it's crazy the electrical system is incapable of isolating a short in a headlight and not allow the vehicle to drive.

 

[KenC]

I think the error looked like the 12v was disconnected, so you got low voltage errors. It seemed the light error was a result of the low voltage. Interesting that they replaced the headlight. Would be interesting to see the invoice. I'd also keep tabs on that 12v. When was it changed?

 

[AlanSubie4Life]

When was it changed?

This is a 2022 so it's a Lithium "12V" (you can also tell from the warning message). Hopefully never needs changing!

 

[davewill]

These days, headlights aren't just simple lights that are turned on and off. They are smart devices that are connected to the internal control bus of the car. As a result, when they malfunction, they can take a large amount of the car's functionality with them.

It's not just Tesla, either:

How This 2018 Ford F-150's Faulty Taillight Turned Into a $5,600 Repair

 

[ajrettke]

Crazy that it just cannot be isolated though and flag as a caution…not make it so I cannot drive! I understand automated braking and many other sensors can be impacted…

 

[cbdream99]

It could also be some safety features to prevent you from driving without headlights. See this fellow having very similar problem.

 

[davewill]

Crazy that it just cannot be isolated though and flag as a caution…not make it so I cannot drive! I understand automated braking and many other sensors can be impacted…

Of course, it can be (and to some extent is) done. That's why cars don't have a single CAN bus controlling everything, but instead separate busses that handle different types of car modules. Being a shared bus, any module on the bus has the potential to take the whole bus down.

However isolating with a high degree of granularity is difficult and has the potential to introduce more points of failure.

 

[XPsionic]

Crazy that it just cannot be isolated though and flag as a caution…not make it so I cannot drive! I understand automated braking and many other sensors can be impacted…

You're absolutely right, I don't care what kind of headlights Tesla decides to use, it's simply stupid and ridiculous that a broken headlight could cause the car to be immobile. People who are saying how difficult it might be to isolate such system is missing the point. If Tesla can't keep a car moving with a headlight fault, they've designed it wrong, period.

Very strange that all the 12v faults pointed towards a connection issue with the low voltage battery, yet the fix is simply replacing headlight and no mentions of checking or tightening cables to the 12v.

 

[mongo]

So we've had some heavy rain for 2 days or so (DC Area). Never had any issues until yesterday morning when I tried to take my kids to school. From absolutely no errors, I got the screenshot below:

Obviously couldn't drive the vehicle so it got towed and this morning they fixed it. But it was simply replacing the headlight. Are our cars so vulnerable to basic errors they completely shut down? The technician note simply said the concerns were validated and the headlight replaced which was bringing down the system.

It seems to me it's crazy the electrical system is incapable of isolating a short in a headlight and not allow the vehicle to drive.

When did these errors occur? When driving, or when you first got in the car?

The left headlight sits on it's own power feed so in the event of a hard short, it would be disabled. Beyond that, it's a smart device and is controlled over the LIN bus.

Possibly, it had a fault in which it activated the lights which drained the 16V battery to the point where it self protected and shut off. Once that happened, the headlight also reset. The PCS normally keeps the 16V battery charged, but it may be power limited while the cars is asleep. The headlight resettingmay have allowed the PCS 16V supply to run the contactors and wake the car up.

 

[Maki22]

So we've had some heavy rain for 2 days or so (DC Area). Never had any issues until yesterday morning when I tried to take my kids to school. From absolutely no errors, I got the screenshot below:

Obviously couldn't drive the vehicle so it got towed and this morning they fixed it. But it was simply replacing the headlight. Are our cars so vulnerable to basic errors they completely shut down? The technician note simply said the concerns were validated and the headlight replaced which was bringing down the system.

It seems to me it's crazy the electrical system is incapable of isolating a short in a headlight and not allow the vehicle to drive.

I had the same thing happen with my 2020 Model 3.

The electronics in the driver side headlight failed and started to produce allot of noise on the bus. It prevented the car from communicating with the 12V battery system, charging system, high voltage battery system and windshield wipers.

Tesla had to replace the headlight, and 12V battery. They had also ordered a new high voltage battery, but didn't replace it since everything returned to normal after replacing the headlight.

 

[PianoAl]

Yesterday I saw a Tesla driving with only one headlight on.

 

[Sti-g]

I saw one with no headlight on. It was like magic.

 

[ajrettke]

I had the same thing happen with my 2020 Model 3.

The electronics in the driver side headlight failed and started to produce allot of noise on the bus. It prevented the car from communicating with the 12V battery system, charging system, high voltage battery system and windshield wipers.

Tesla had to replace the headlight, and 12V battery. They had also ordered a new high voltage battery, but didn't replace it since everything returned to normal after replacing the headlight.

The morning after driving in the rain....I did hit a large 2" puddle when driving to grocery store. No issues or alerts, got grocery's came home and parked and plugged in. The following morning when I got in is when it lit up like a Christmas tree with errors.