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Tesla BMS_a035 / BMS_a151: Vehicle May Not Restart Fix

By the EV Fix Guide editorial team · Updated October 24, 2026 · How we estimate costs

Quick answer

BMS_a035 and BMS_a151 mean the car detected reduced electrical isolation between the high-voltage system and the car body. The car may refuse to charge or drive. Common causes are water getting into a high-voltage connector or component, a damaged cable, or an internal battery fault. At a Tesla Service Center this typically costs $0 (Under warranty) / $300 - $3,000 (Component repair) / $12,000 - $20,000 (Pack replacement). An independent shop charges about $300 - $2,500 (Isolation diagnosis and component repair) — potential savings of 30% - 80%. Do not attempt this at home.

BMS_a035 / BMS_a151: Vehicle May Not Restart - High Voltage Isolation Fault

Symptoms

'Vehicle may not restart - Service is required' alert with code BMS_a035 or BMS_a151
Charging refuses to start or stops
Often appears after heavy rain, a car wash, deep puddles or underbody damage
May clear on its own and come back later

Repair cost: Tesla vs independent shop vs DIY

Option	Typical cost (USD)
Tesla Service Center	$0 (Under warranty) / $300 - $3,000 (Component repair) / $12,000 - $20,000 (Pack replacement)
Independent shop	$300 - $2,500 (Isolation diagnosis and component repair)
DIY	Not possible at home (High-voltage hazard)
Potential savings	30% - 80%

Ranges are US estimates compiled from owner reports and shop quotes; prices vary by region, model year and parts availability. Report your price.

Can an independent shop fix it?

Isolation faults need high-voltage diagnosis to find which component is leaking (pack, heater, compressor, charger, cables). Inside the battery warranty go to Tesla. Out of warranty, independent EV high-voltage specialists can test each component and replace only the faulty one, which is often far cheaper than a new pack.

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How professionals repair it

Safety warning: This is a high-voltage safety fault. Do not open any orange cables or components. Tesla says not to charge the car with BMS_a151 active, and to stop using it if you smell, hear or see anything unusual near the battery.

Tools a shop uses

Tesla app (to log alerts and book service)
Notes on weather and what happened before the alert appeared

Steps

Do not try to charge the car while BMS_a151 is active; Tesla's manual says so explicitly.
If you notice smoke, a burning or sweet chemical smell, hissing or visible damage near the battery, leave the car, move away and call Roadside Assistance.
Write down when the alert appeared: after rain, a car wash, a flooded road, or hitting debris are all useful clues for the technician.
If the alert clears and does not return over the next few drives, keep an eye on it but you may not need service.
If it persists, book service. Check your 8-year battery and drive unit warranty first.
Out of warranty, ask an independent EV specialist for an isolation test that names the faulty component before accepting a pack replacement quote.

Pro tip: Isolation faults are frequently caused by moisture in a single connector or component, not a dead battery. A proper component-by-component test is what separates a few-hundred-dollar repair from a five-figure one.

Had this fixed? Share what you paid

Owner-reported prices keep these ranges honest. We publish only anonymous averages and email you the results.

Frequently asked questions

How much does it cost to fix a BMS_a035 or BMS_a151 isolation alert on a Tesla?

Tesla Service Center: $0 (Under warranty) / $300 - $3,000 (Component repair) / $12,000 - $20,000 (Pack replacement). Independent shop: $300 - $2,500 (Isolation diagnosis and component repair). DIY: Not possible at home (High-voltage hazard). Typical savings versus the service center: 30% - 80%.

Can I fix a BMS_a035 or BMS_a151 isolation alert myself?

No, this is not a safe DIY job. This is a high-voltage safety fault. Do not open any orange cables or components. Tesla says not to charge the car with BMS_a151 active, and to stop using it if you smell, hear or see anything unusual near the battery.

Can an independent shop fix a BMS_a035 or BMS_a151 isolation alert instead of Tesla?

Which Tesla models are affected by a BMS_a035 or BMS_a151 isolation alert?

This issue is reported on the Tesla Model 3, Model Y, Model S and Model X.

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Related guides

This guide is for information only. High-voltage components (orange cables) can be lethal — leave them to trained technicians. Not affiliated with Tesla, Inc.