Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

'16 P100D- Isolation errors

This site may earn commission on affiliate links.
Hi all,

I have started down the path to inspect and repair my HV battery on one of my X's.
125K miles. LDU replaced in 2023.

It started out as intermittent external isolation which would put vehicle in limp mode. Eventually it showed up as internal and obviously the car refused to start.
The internal ISO was always about ~2300 when the car would start and while driving it would drop to 8-900. Eventually when it went to full internal, the internal ISO was 2K and contactors would never close. During this time I had completely powered the vehicle down. I booted up a few times and checked the ISO- each time it dropped further. Each time one observation I had was the coolant pumps spinning. On one of the power ups it dropped to 200Kohms.

I have dropped battery, removed the hump and BMS covers, inclusive of all umbrellas. During this time the pyro replace alert also came up. For two weeks the battery sat outside the vehicle with the hump and bms cover plus umbrellas removed. I finally got the batter tool connected yesterday and probed the battery outside the car. It was 200Kohms. The pack is at 54% so I started the bleed off process. Today ISO is at 2300 and growing. How does it go from 200 to 2K in a day for internal yet have no change for 2 weeks. External iso is at 3.9M@500V.

Is that something that others have seen?
Has anyone seen a case where every 'indicator' part is dry only to find water inside the main bay?
In the battery tool:

When is Isolation Issue set to True?
When is it cleared?
 

Attachments

  • IMG_0246.jpg
    IMG_0246.jpg
    100.5 KB · Views: 18
  • IMG_0248.jpg
    IMG_0248.jpg
    78.3 KB · Views: 13
u need to find the source of isolation issue
usually its water n should see signs of moisture under hump..
if its dry then it could be BMS board itself but its not very common
post all the codes from service mode
no clue what 'indicator' parts u talking about...

have a look here in case its helpful
 
"indicators" = droplets of moisture in fuse box, umbrellas or umbrella holes.

I've seen your thread. extremely useful. It's been a few weeks, went on vacation, tore into it yesterday and today.
ISO grew from about 2300 to 2500 while I was away. (main cover on, BMS cover, hump cover and umbrellas removed)
Pulled the main cover off yesterday, (FWIW - Oscillating tool make quick work of this! Highly recommended- 15 minutes to open both sides)

ISO was about 2650 this morning.
I started pulling modules and checking them. The two rear modules on the drivers side had some mild discoloration ( as if they may have had moisture at some point) on the bottom but no visible moisture. Everything else dry as can be. There was mild rust on the main cover between the BMS cover and the rear driver module.
The umbrellas were definitely filthy - a few I'd say almost clogged or maybe even clogged. Currently fighting with Tesla EPC to ship the correct replacements. I ordered the 'set', they sent one ganged valve assembly. I ordered the mounting bolt kit (about 26 bolts). They literally sent a bolt. Vehicle is a late '16 build with the fuse on bottom.

Anyway, now ISO is over >3000 Kohm. I did start to question if the BMS is good but it appears so. It responds well to all inquiries using the tool. Visual inspection- it looks immaculate. If anyone knows where the resistors are that are used in the ISO measurements I'd be very appreciative of their location or reference designators on the PCB.
FWIW - after purging the coolant I also pressurized the coolant lines in the battery to about 6PSI, and it held.

@brainhouston What did you end up sealing with? The work time for Threebond 1216E is too quick for me, even with 1 helper I dont think we can make it with that.

Codes were:
BMS_f123
BMS_w123
DI_w062
12V not supported.( obviously caused by contactors not closing)

IMG_0417.jpg
 
  • Like
Reactions: brainhouston
...
@brainhouston What did you end up sealing with? The work time for Threebond 1216E is too quick for me, even with 1 helper I dont think we can make it with that.

Codes were:
BMS_f123
BMS_w123
DI_w062
12V not supported.( obviously caused by contactors not closing)
i used sikaflex grey 221
and yeah i had f123 as well n i did find how water got in n where it grounded..
i'm not sure about iso resistors but i recall its a long string of them on BMS pcb since they have to drop 400v to very tiny current...
i believe wk057 had a pic somewhere on his site or here...

iso should be about 3Mohm with open contactors n about 1.5 with closed
 
  • Like
Reactions: calimark
I connected it back to the car ( no cover, no coolant). Error still there although ISO was 2600+. Started freaking out until I was reminded this is a latched error. Cleared it with toolbox and beep beep beep.....no go! Got HVIL error....oops forget the fireman's loop. Connected that, still no go. Remove battery, try again same thing. Eventually gave up and pulled battery. Traced the wiring and realized that the middle PIN on the HV mate connects a wire that's part of the HVIL I probably needed that rear middle bolt installed to make it fully seat. Anyway with all the fussing, I managed to damage the plastic housing on the BMS side so now waiting for a replacement.

I also took the opportunity to update and replace the fuse, That went well.

Next step: Seal up, pressure test then reinstall when the housing arrives,
 
  • Like
Reactions: brainhouston
I guess next steps wont happen now. I'm truly questioning my sanity now. I hope someone else might have ideas ( 150+ views, please someone have an idea).
The plastic part for the HV connector came in. Pulled the contactor assembly, fixed that and reinstalled. Decided to check ISO. It has been about 1.5 weeks since testing in car uncovered. The pack was sealed (minus the umbrella valves), and was sitting in the same place in the garage with the same weather. Hot n rainy outside. I have now run hot air thru 7 modules today with zero meaningful change in ISO. My ISO is reading 2-300 K OHM.

From the bus bars (@contactor) I measure:

Top Bus Bar(-ve) to case : 239-249V (It fluctuates each time the Tesla battery tool tries to refresh the stats)
Bottom Bus Bar(+ve) to case : 98 to 110V (It fluctuates each time the Tesla battery tool tries to refresh the stats)
Top to Bottom Bar: 359V stable, zero fluctuations.
Battery Tool reads : 359V stable
ISO: 2xx-368K Ohm ISO

Every cap was put back on the modules including the top mica sheets etc.
 
Is bms connected?
With that 4 pin connector that goes from both sides of contractors to bms, you'll get voltage to ground like ur getting, from both sides of hv, that's by design, this is how bms measures iso.
Also u really can't measure iso with voltages present, my iso meter won't even measure anything if it sees more than 30v on leads...
 
Is bms connected?
With that 4 pin connector that goes from both sides of contractors to bms, you'll get voltage to ground like ur getting, from both sides of hv, that's by design, this is how bms measures iso.
Also u really can't measure iso with voltages present, my iso meter won't even measure anything if it sees more than 30v on leads...
Agreed, hence why I'm trying to understand where/what are the points on the BMS. With those I could measure the voltages on the 'actual BMS' and perform the calc. I definitely found the 1st resistor in the set. Either way I'm fairly confident the BMS is still 'OK' and am starting to conclude this thing is super sensitive to humidity fluctuations.
 
So this saga is sorted out for now. I observed a few behaviors with the ISO fluctuations I saw with pack out the car. Anyway when it was sealed up with valves it settled around 2400K ohm ISO.

I had a hell of a time dealing with BMS_w126_HW_BMS_Blind_Mate, along with BMS_w036 and BMS_f036. W126 as it says is the HVIL pin thru the battery, make sure to clean your terminals with isopropyl as recommended. I dropped the pack about 6 times troubleshooting those codes, eventually taking the BMS cover probing every LV pin back to the actual BMS PCBA. I even jumped the battery pin and was able to see w126 disappear, but the others remained.
Only after walking away depressed, did my brain clear and I remembered that I changed the battery heater but was not able to plug in the HV as the car was too high to reach it. Snapped that in and finally there was life.

After that, I ended up with PTCCanTmo error and no front heat. The heat had definitely been weak before this ISO incident, but somehow it finally went kaput.

So now in car, contactors open ISO about 2450 +/-. Contactors closed but car parked its about 900. This is with the blown PTC removed and its HVIL jumped.
Front and rear AC screaming, battery heater running for ludicrous plus (40mins), and drive engaged resulted in fluctuations from 880-1100. I've had a previous P90D and seem to recall that thing ran perfectly fine with similar numbers but I find it weird that with contactors closed and nothing 'ON' it drops so much.
ISO for everything at tested at the HV battery big blades were > 3.8Mohm on both legs to ground.
Any thoughts?