Hi,
I just recently had an issue on my 2022 Model X Plaid and I'm looking for some help from people more experienced on debugging this kind of complex issue.
Last saturday I started a drive around the city, and after parking and putting on reverse, I got the following errors: BMS_a170 and BMS_a027
[Moderator note: image redacted per poster's request]
Entering Service Mode gave a little more insight on what happened: The car started measuring Isolation Degradation (BMS_a142) since I opened the door in the morning, even before starting my drive. After a few counts of the error, it showed the BMS_a170 and BMS_a027 errors that I had seen on the panel.
The car since then entered "limp mode" with limited power and no regeneration.
When diving deeper in Service Mode information, I found that the "External Isolation Resistance" was barely below the "green" limit of 1000 kOhm, it was at 970 kOhm.
After that, I took the car home, tried everything from a soft reboot, a Software Reinstall from Service Mode, letting it sleep and get back online, turning off power (disconnect LV battery and emergency loop), keeping the A/C off for a while, but the isolation resistance remains on that level, varying from 800 kOhm to 1050 kOhm.
I have the car here in Brazil, so accessing Tesla Service is not an option. The car currently is with the best service center for Teslas in Brazil (eZeni car service), and they are still trying to debug the issue. They ran the Toolbox 3 on it, but it still only shows just the same alerts. No car module seems to have any other error messages.
The car worked fine and perfectly for almost an year. The only issue it had was with the side passanger airbag, which had one wire completely ruptured that was fixed by my local service center a few days before the incident.
After discussing it with the local service center, from our understanding this failure can come from one of these sources:
1) HV Cables
2) HV Connectors
3) PCS
4) A/C
5) Motors
Which are the systems that use the High Voltage. We believe that it is less likely to be an issue with the last 3 options, since there are no other alerts from any of those modules, that have their own sensors and specific errors, which leaves us with a potential issue on the cables or connectors.
Since humidity is one of the possible sources of cable HV Isolation degratation, we realized that the error started just in the morning after we washed the car in the late afternoon. It might be a coincidence, but it was the first time the car was washed with a Car Pressure Washer. It had always been washed without pressure before that. So we suspect we might have a connector defect (crack, broken watertight isolation, etc) that allowed humidity to enter a connector after the wash and is giving us this error now.
Unfortunately I don't have any records of the measured Isolation Resistance that we had on the car before the error. It could be sitting just above 1000 kOhm and the car wouldn't let me know. Comparing to other Model X owners, it should be higher that 3000 kOhm.
We already did a quick visual inspection of the cables and connectors without touching them, and there is no visible defects. We are now proceding to disabling the High Voltage and starting disconnecting the cables to inspect them all.
If anyone here has any experience with this kind of error, or any tips that could help us track down the problem, I would appreciate the help!
I just recently had an issue on my 2022 Model X Plaid and I'm looking for some help from people more experienced on debugging this kind of complex issue.
Last saturday I started a drive around the city, and after parking and putting on reverse, I got the following errors: BMS_a170 and BMS_a027
[Moderator note: image redacted per poster's request]
Entering Service Mode gave a little more insight on what happened: The car started measuring Isolation Degradation (BMS_a142) since I opened the door in the morning, even before starting my drive. After a few counts of the error, it showed the BMS_a170 and BMS_a027 errors that I had seen on the panel.
The car since then entered "limp mode" with limited power and no regeneration.
When diving deeper in Service Mode information, I found that the "External Isolation Resistance" was barely below the "green" limit of 1000 kOhm, it was at 970 kOhm.
After that, I took the car home, tried everything from a soft reboot, a Software Reinstall from Service Mode, letting it sleep and get back online, turning off power (disconnect LV battery and emergency loop), keeping the A/C off for a while, but the isolation resistance remains on that level, varying from 800 kOhm to 1050 kOhm.
I have the car here in Brazil, so accessing Tesla Service is not an option. The car currently is with the best service center for Teslas in Brazil (eZeni car service), and they are still trying to debug the issue. They ran the Toolbox 3 on it, but it still only shows just the same alerts. No car module seems to have any other error messages.
The car worked fine and perfectly for almost an year. The only issue it had was with the side passanger airbag, which had one wire completely ruptured that was fixed by my local service center a few days before the incident.
After discussing it with the local service center, from our understanding this failure can come from one of these sources:
1) HV Cables
2) HV Connectors
3) PCS
4) A/C
5) Motors
Which are the systems that use the High Voltage. We believe that it is less likely to be an issue with the last 3 options, since there are no other alerts from any of those modules, that have their own sensors and specific errors, which leaves us with a potential issue on the cables or connectors.
Since humidity is one of the possible sources of cable HV Isolation degratation, we realized that the error started just in the morning after we washed the car in the late afternoon. It might be a coincidence, but it was the first time the car was washed with a Car Pressure Washer. It had always been washed without pressure before that. So we suspect we might have a connector defect (crack, broken watertight isolation, etc) that allowed humidity to enter a connector after the wash and is giving us this error now.
Unfortunately I don't have any records of the measured Isolation Resistance that we had on the car before the error. It could be sitting just above 1000 kOhm and the car wouldn't let me know. Comparing to other Model X owners, it should be higher that 3000 kOhm.
We already did a quick visual inspection of the cables and connectors without touching them, and there is no visible defects. We are now proceding to disabling the High Voltage and starting disconnecting the cables to inspect them all.
If anyone here has any experience with this kind of error, or any tips that could help us track down the problem, I would appreciate the help!
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