1. Introduction
In this guide, you will get following information:
- How to diagnose the exact cause of the alert
- Possible causes for the alert
- How to fix and clear
- Estimated cost to resolve the alert
- How to get quick, easy and affordable remote support (Whats App +49(0)15226242038)
Remote Diagnosis and support to clear alerts
Feel free to contact us on Whats App +49(0)15226242038. We are happy to assist with remote diagnosis and provide support to clear alerts at affordable prices.
1.1 Why its important to have isolation in electric car?
High Voltage systems are mounted on car chassis. There must be a minimum electrical isolation/resistance in between High Voltage System and Car Chassis to ensure safe car operation.
There is monitor which is installed in battery, which measure periodically the resistance between the high voltage conductors and chassis.
1.3 Isolation Test?
BMS performs the isolation test. If it detect low isolation, it triggers the isolation alerts. After getting couple (number of counts) of alerts, car may not start.
1.3 Type of Isolation
There are internal and external isolation.
1.3.1 Internal Isolation
Internal isolation is related to High Voltage Battery and possible code could be BMS_a123
- BMS_a123_SW_Internal_Isolation
1.3.2 External Isolation
External isolation is related to High Voltage Component issue and possible code could be BMS_w035, BMS_a151
- BMS_a035_SW_Isolation
- BMS_w035_SW_Isolation
- BMS_a151_SW_external_isolation
1.4 What will happen?
2. Diagnosis
This alert could come because of isolation issue. It need to check additional alerts to find out the cause of this alert.
It could be possible to find out the exact cause via Remote Diagnosis, Service Mode.
2.1 How to check additional alert
Additional alerts can be checked via Remote Diagnosis or Service Mode.
If you need support to check additional alerts, feel free to Connect Us Phone/Whats App +49(0)15226242038
2.2 Remote Diagnosis
Remote diagnosis will provide the exact cause of the alert. We offer Remote Diagnosis with affordable prices. Please contact us or book a remote diagnosis. Book Remote Diagnosis
If you have any question about remote diagnosis (how it work), please refer our another guide
If you need support, feel free to Contact Us Phone/Whats App +49(0)15226242038
2.3 Service Mode
In some cases, it can be be possible to find out the exact cause of the alert in Service Mode with the help of following details:
- Service Alerts in Service Mode
- Self-Diagnose in Service Mode
How to check service alerts in Service Mode
- On the touchscreen, click Controls (vehicle icon) > Software
- Touch and hold the large word "MODEL" for 4 seconds and then release.
- Enter "service" as access code (password).
- Clicking Service Alerts to view active and recent alerts. If there is any issue, it will appear in Service Alerts.
For more information, please refer another guide (How to do enable Service Mode) Link
Service Mode > High Voltage > HV Systems
If everything is good. You will see green circles, Contactors are clsoed, Internal External values in green.
In case, if there is any issue with High Voltage components. You could be able to see low resistance value and red circle, Contactors are open.
You could run thermal test. Thermal test result might give you an indication, which part could be causing isolation alert. A/C compressor, PTC heater could be most likely causing the alert.
Service Mode > Thermal > Test
BMS Isolation Resistance
BMS_ISOLATIONRESISTANCE
BMS_STATE
BMS_CONTACTORSTATE
THC_COMPCONSUMPTIONPWR_W
PT_THC_PTCDUTYFB_PERC
PT_THC_BATTERYHEATERPCT
PT_DI_MOTORRPM
PT_DI_STATE
PT_DI_GEAR
Please send us Test result screenshot. We will be happy to help you.
If you need support. Please send us Service Alert Screenshot via Contact or Whats App +49 (0) 15226242038. We will be happy to help you to explain alert and how could be fixed, cost, support for fixing if possible online support or to organize an appointment with independent affordable workshop.
Depend on alert/fault code, car might need to be repaired/serviced.
3. Alert Code
Some of most common possible alert code.
You might have received one of following alert.
You might have received one of following alert.
- BMS_a035_SW_Isolation
- BMS_w035_SW_Isolation
- BMS_f035_SW_Isolation
- BMS_a151_SW_external_isolation
- BMS_f151_SW_external_isolation
- BMS_a123_SW_Internal_Isolation
BMS_w035, BMS_a035, BMS_f035
- BMS_a035_SW_Isolation
- BMS_w035_SW_Isolation
- BMS_f035_SW_Isolation
- There is an external or internal isolation alert while pack contactors are closed.
- The BMS detects that isolation is below the minimum threshold while contactors are clsoed.
- Danish Text: Køretøj kan muligvis ikke startes igen
BMS_f151
- BMS_f151_SW_external_isolation
- BMS has detected that HV isolation is too low while contactors are closed
- BMS_w151_SW_external_isolation
Please send us your "Service Alert" Screenshot via Contact or Whats App +49 (0) 15226242038. We will be happy to provide you support to fix/reset alert with affordable prices without going to service center which could save your money and time. We can help you to explain the possible cause, how to diagnose, how to fix/reset/repair etc.
4. Steps to Clear Alert
Some alerts may be resolved by restarting the system, updating the software, reinstalling the software, repairing the hardware, or performing a reset.
4.1 Restart System
Some alerts may be resolved by restarting the touchscreen or powering of the car.
Restart the Touchscreen
First, you can try a soft reset (touchscreen reset).
How to perform a Soft Reset (Restart the Touchscreen)
- Shift the car into park.
- Press and hold both scroll buttons on the steering wheel until the touchscreen turns black.
- Wait approximately 30 seconds for the touchscreen to restart.
For more details, please refer another guide on how to perform these steps Link
Powering Off the Car
If a soft reset (touchscreen restart) has not resolved the alert or issue, you can try a hard reset (powering off the car).
How to Perform a Hard Reset
- Shift the car into park
- On the touchscreen, go to Controls > Safety > Power Off
- Wait at least for two minutes without interacting with the car. Do not open the doors, press the brake pedal, or touch the touchscreen etc.
- After two minutes, press the brake pedal or open the door to wake the car (Source Tesla)
4.2 Software clear
Some alert may be related to software bugs or glitches.
Software Bug and Glitches
One possible reason could be software bug or glitches.
- Did you receive this alert after updating recent software version?
- If yes, it could be related to a software bug and may be resolved in a future software update.
- Please send us screenshot of the Service Alert, and we will inform you if it could be related to software bug. Link
Firmware not Updated
One of the main reasons could be that firmware is not updated.
-
Have you checked for the latest software update and installed the most recent version?
- If not, it is recommended to install latest software version.
- Please ensure that your car is running the latest software version.
How to install latest software version
Controls > Software > Update Available
For more details, please refer to another guide how to install the latest software version. Link
5. Hardware Issue
There could be some hardware issue/faulty. Some of common hardware issues could be followings:
There could be issue with Hardware. High Voltage Component/part with isolation breakdown need to identified and faulty/damaged part/parts need to be replaced/repaired.
When diagnosis isolation issue, look for any signs of moisture, physical damages on HV cables, bus bars, and connectors.
One of following high voltage component may have low isolation:
- AC Compressor
- PTC Heater
- Charge Port
- Primary, Secondary Charger
- DCDC
- Front, Rear Drive Unit
- HV Harness/Cables
- Battery Heater
Physical defect of the insulation material
There could be physical damage to High Voltage cables, bus bars, and connectors.
Contamination (Chemical Stresses)
Contamination (of any size, e.g. dust, bolts, etc.), or moisture. Please have a detail look in another guide about Water Ingress/Moisture. Link
- Coolant, water, vapors, moisture etc.
- Oil, dirt, dust etc
Electrical Stresses
- Over voltage, Over current
Mechanical Stresses
- Loose Bolts
- Did you get this alert after recent HV Component repair? If yes, please make sure it is corrected put back as described in service manual.
- Not installed correctly HV Harness
- Please make sure harness routed as described in service manual
- Shorts to resistors or circuitry
- Damaged component related to HV Components (Example IGBT in PTC Heater)
5.1 Drive Unit (Front or Rear Drive Unit)
One of reason could be low isolation issue with Drive Unit.
Model S (2012-2020) Model X (2015-2020) with Large Drive Unit - Liquid ingress into rear Drive Unit
If you have Model S or X with Large Drive Unit. It could be common leakage issue. Please find more details in another guide (How to check, fix etc). Link
You may get some alerts related to DI_ in service alert logs
How to check isolation for LDU Inverter
Please have a look for more details. Link
Drive Unit Repair Repair Guide
More details about drive unit repair in another guide. Link
Insider Tip to diagnose: isolation value will drop when car will be in driving condition. When car will be in park, isolation value may be normal.
Inspect HV Harness
Recent Repair
Did you get alert after recent repair. Please make sure that HV Bolt properly torqued.
500V
| Measurements Points | ||
| LDU | Measure voltage at the B+ and ground, B- and ground, and B+ and B- | More details |
5.2 PTC/Positive temperature Coefficient Heater (Cabin heater)
One of reason could be issue with PTC Heater. Please check more details PTC Heater in another guide. Link
Isolation will drop when PTC Heater (AC) is on.
250V
Which models has PTC Heater
All models produced before 2021.
5.3 AC Compressor
One of reason could be issue with AC Compressor. More details about AC Compressor repair in another guide. Link
250V
5.4 Battery Coolant Heater
One of reason could be issue with battery coolant heater. Please check out more details about battery coolant heater in another guide. Link
Battery coolant heater will activate at supercharger. Did you get this alert when using Supercharger? If yes, please let us know. We can help you.
Isolation value will drop when Battery coolant heater will be ON and OFF (enable/disabled)
One of reason could be that coolant leakage at O-ring sealant is damaged.
500V
5.5 HV Harness/Cables
When diagnosis isolation issue, look for any signs of moisture, physical damages on HV cables, bus bars, and connectors.
Inspect connectors for any signs of contamination or moisture.
One of reason could be issue (damage/faulty etc.) with High Voltage Harness.
5.6 Charge Port
One of reasons could be charge port or high voltage harness in between charge port to HV Battery.
1000V
5.7 Charger (Primary/Secondary)
5.8 DCDC
Recent Repair/Service
Did this alert pop up after recent repair/service? If yes, please let us know which repair/service was done recently. Some alerts could pop up if repair/service is not done in proper way. If system/alert has not be reset. Did you use aftermarket/used part?
Poor connection: Did you unplug any high voltage cables? If so, please make sure connected properly.
Voltage for Testing
PTC heaters and A/C compressor 250V
All other components - 500V
Charge ports only - 1000V
Isolation Resistance
| Measurements Points | Expected isolation Resistance | |
| DC-DC | DCDC HV+ to Ground | > -- MOhm |
| DCDC HV- to Ground | ||
| LDU | Measure voltage at the B+ and ground, B- and ground, and B+ and B- | More details |
Model 3/Y
| Charge Port | More details |
Find and book best Workshop to fix Isolation issue
If you are looking for Workshop who is expert to fix such issue with best price. Please contact us with details in which country/city, are you looking for. Contact to Fix Isolation Issue
Remote Support/Help
In case if you need any support or have any question. We will be happy to provide you Online/Remote Support. Please Contact Us.
5. Cost
Cost could vary depend on issue, type of workshop, location. If you are looking for online support or affordable independent workshop. Please free to contact us or have a look in Price List
How to clear
Service Mode - High Voltage - Clear isolation counters
PROC_BMS_X_CLEAR-ISOLATION-ALERT-COUNTERS
Tools needed
Some of following tools are needed to check isolation
- PPE
- Insulation Multimeter
- HV gloves
Find more details link
FAQ
1. Can i reset the alert?
It is recommend not do reset alert as long issue is not repaired.
2. Can I do at Local Workshop, Independent Tesla Workshop?
Yes, you can. However, please make sure that workshop knows how to work to Tesla Cars. If local workshop need any support. Please feel to contact us. We will be happy to provide online shop. You can also find workshop in our Workshop Locator.
3. Can I do it/repair yourself/myself (DIY)?
Some of repair could be done at DIY. In case, if you needed Tools, Know-How, Time etc. Please feel to contact us. We will be happy to provide you online support.
Note: Please do not work with high voltage components. If you do not need needed/proper Tools, Know-How etc. It could be dangerous.
4. Mobile repair service?
In some of cases, we could also provide mobile services. Please feel to contact us where are you located and what kind of repair are you looking for.
5. Car not under warranty, salvage, accident, flood, modified cars?
It is highly recommended to perform repair with independent workshop to save money.
6. Car under warranty?
In case if your car is under warranty. It is recommended to perform certain repair works (HV Components, ADAS etc) with OEM during warranty period. Wear and Tear Part Repair could be done with independent workshop to save money. Please read more details in another guide. Link
7. Alert still appearing after repair?
There could be many reasons. Some of reasons could be please make sure that repair was done in correct way, did you restart system after performing repair? did you Reinstall Firmware? Still appearing alert: Please free to Contact Us. We will be happy to provide you online support. Phone/Whats App +49(0)15226242038
8. Which tools needed for diagnosis
You need insulation multimeter (Fluke 1507, 1587), PPE, HV Gloves, KET Dummy Plugs for DCDC HV Connectors Part Number 1025041-00-A.
9. What is isolation resistance?
The electrical resistance between two conductors separated by an insulating material.
What is BMS (Battery Management System )?
"Battery Management System is a printed Circuit board assembly, which communicates with the BMSs (each module) and the powertrain/vehicle.
Vehicle HV Disablement Procedure
Please read more details. Link
Chasis Ground Point for Testing?
It is important to find good chasis ground for testing and good/correct testing results.
Source : Tesla NHTSA, Isolation Procedure Isolation/Insulation Test
