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

High Voltage Interlock Loop (HVIL) Issue - Questions

cab

Active Member
Sep 5, 2013
1,033
721
Grapevine, TX
Hello All,

So a week or so ago, our 2013 P85 threw a slew of errors at home as we went to leave (i.e. Unable to Drive: Voltage supply too low; Electrical system power reduced: Vehicle may shut down unexpectedly; Power reduced: Vehicle systems shutting down; Vehicle may not restart: service is required). Shortly thereafter all of the screens went blank. Some sleuthing here on TMC revealed it was likely tied to the 12 volt system somehow. Anyway, I popped off the nosecone and checked the 12V battery from the two poles behind the nosecone (hooray for pre-refresh) - it showed 11.4 volts if I remember correctly. I popped on my 12V charger and the screens immediately popped back up. I let it charge overnight (both on the 12V charger and plugged into the the EVSE) and the error messages did not return. I checked the battery each morning for the next couple of mornings and it was consistently around 12.6V after sitting overnight w/o being driven...lower than I might like, but it seemed ok.

Anyway, I was able to drive it to the service center (no errors) and dropped it off. After a couple of days they indicated they wanted to replace the DC to DC converter (over $3k). The invoice explicitly indicates:

"Reviewed vehicle logs and found the HVIL to be intermittently open. Performed diagnosis of the HVIL circuit and found that the lid switch on the DCDC is intermittently open. Recommend replacement of the DCDC for the second generation retrofit as the first generation are no longer available."

After some additional research on the DC2DC converters here on TMC and elsewhere I see the fuse issue isn't uncommon, but in my case that doesn't sound like the issue (a fuse would be a lot more binary). I also see references to the "lid switch" on the HVJB, but I haven't seen any references to a lid switch on the DC2DC unit so my questions are:

  1. Basic Question - Is the "lid switch" referenced here just a simple magnetic reed type switch that is used to detect that the "lid" (i.e. case cover) is actually on/closed/sealed up? (i.e. the "fancy" version of what we've all seen on washing machine and dryer lids for years)?
  2. Is there a lid switch on the DC to DC Converter? - I haven't seen it listed or referred to in any schematics so I'm just not sure there is one (although it might make sense that there would be)?
  3. Any other ideas? I have seen at least one tech bulletin referencing the 4 or so connectors that actually connect to the DC to DC converter (hvac, heater, input, etc.) and even a TSB where there is a new harness for those connectors (essentially, sounds like the pins were a bit short in some cars). Maybe someone like @Ingineer will chime in (hint, hint).
I am picking up the car today (w/o them repairing it), while I research this further. Honestly, while I believe there could very well be an issue in the HVIL, I'm not 100% sure the DC to DC converter itself is the issue.

Thanks all and happy new year!

Anyway, m
 
  • Like
Reactions: KyleDay and rickyjb
Mar 1, 2018
120
145
San Marcos, CA
Good questions. I looked at the schematics for rear wheel drive Model S built before 9/2015, and the HVIL page only shows the 2nd generation DC-DC converter with the separate front junction box; nothing about the 1st generation DC-DC. I wonder if that's leading the technician down the wrong path.

The schematics indicate that HVIL protects the 2nd generation DC-DC, and it shows a lid switch in the HVIL circuit on the adjacent front junction box.

Your car has the 1st generation DC-DC converter with the integrated front junction box, which wasn't designed to be opened easily. My guess is that it doesn't have a lid switch, but it would still be connected to the HVIL.

An intermittent HVIL problem is definitely plausible, though it's not explicitly "lid switch" related.

I had forgotten about the bulletin about the too-short pins, but that is certainly possible. If you can get your hands on that bulletin, you could see if your car is in that date range.
 

Huachipato

Member
Jul 16, 2019
210
156
Murphy, TX
I got all those error messages this morning. For me it seems to be triggered after I remotely turn on the climate control on cold days and let it warm up. Picture from this morning. I didn't even pull out the garage before all the errors went away.

PXL_20210112_132554364.jpg


I should add the 12V was replaced by Tesla back in August if I recall correctly
 

cab

Active Member
Sep 5, 2013
1,033
721
Grapevine, TX
Good questions. I looked at the schematics for rear wheel drive Model S built before 9/2015, and the HVIL page only shows the 2nd generation DC-DC converter with the separate front junction box; nothing about the 1st generation DC-DC. I wonder if that's leading the technician down the wrong path.

The schematics indicate that HVIL protects the 2nd generation DC-DC, and it shows a lid switch in the HVIL circuit on the adjacent front junction box.

Your car has the 1st generation DC-DC converter with the integrated front junction box, which wasn't designed to be opened easily. My guess is that it doesn't have a lid switch, but it would still be connected to the HVIL.

An intermittent HVIL problem is definitely plausible, though it's not explicitly "lid switch" related.

I had forgotten about the bulletin about the too-short pins, but that is certainly possible. If you can get your hands on that bulletin, you could see if your car is in that date range.

@ElectricTravel Thanks. Found the bulletin, but it applies to cars built before mine(My car was an August build, and bulletin applies to cars built before April 8, 2013) - https://static.nhtsa.gov/odi/tsbs/2014/SB-10052449-1693.pdf

We haven't driven the car a ton (Covid-life) since I got it back, but the errors have yet to re-appear. I'm sure there is a lurking issue, but not at all sure how to trace this one down.

@Huachipato - very interesting AND it is possible my scenario may mimic yours as I've been thinking about this same thing for a while as a possible trigger. As a fellow Texan, I pre-condition regularly in our blazing hot Summers, but comparatively rarely in the Winter. Before this issue cropped up for me I remember pre-conditioning to warm the car to go somewhere, but I THINK I forgot about it and left it pre-conditioning a while and then ultimately didn't go out as planned (I noticed the pre-conditioning was still going a while later). I know this all sounds nebulous, but working from home and with Covid we often don't go anywhere for days at a time so the timing of all this is a bit foggy. In short, the first time we did go somewhere it may have been after that pre-conditioning session and that may have triggered it. It make me wonder if something in the heater circuit could be causing an issue. I think the PTC (basically, a fancy electric heater) may actually run off of 12 volt and, of course, during pre-conditioning I assume the DC to DC converter is engaged to ensure enough juice is present for the heater, but who knows (maybe it cycles on/off/etc). As my heater does work, the PTC isn't "dead" obviously and the DC to DC fuse for it clearly isn't blown, but I wonder if something in the PTC is drawing a bit higher current and taxing the 12V battery....hmmm.

I definitely need to try pre-conditioning again to see if I can "force" the issue (of course have so much going on today, I can't try it out right now).
 

rooter

Member
May 13, 2018
732
904
Edmonds, WA
cab: No, this isn't an HVIL issue. Look at your original symptom. If this recurs, Tesla was on the right track.

Huachipato: Without error codes in Factory mode I can't tell for sure, but could be battery. I know you said, "I should add the 12V was replaced by Tesla back in August if I recall correctly" but that sentence doesn't make any sense.
 

cab

Active Member
Sep 5, 2013
1,033
721
Grapevine, TX
cab: No, this isn't an HVIL issue. Look at your original symptom. If this recurs, Tesla was on the right track.

Huachipato: Without error codes in Factory mode I can't tell for sure, but could be battery. I know you said, "I should add the 12V was replaced by Tesla back in August if I recall correctly" but that sentence doesn't make any sense.

Rooter, I'm not sure I follow. You indicate this is NOT an HVIL issue, but then say Tesla (who said my issue IS an HVIL issue...tied to the DC2DC lid switch...which likely doesn't actually exist) was on the right track?
 

rooter

Member
May 13, 2018
732
904
Edmonds, WA
Rooter, I'm not sure I follow. You indicate this is NOT an HVIL issue, but then say Tesla (who said my issue IS an HVIL issue...tied to the DC2DC lid switch...which likely doesn't actually exist) was on the right track?
Ok so it was Tesla that found that error. Note that the base problem is that the DC-DC converter did not charge the battery, because it thought its lid was loose or off. And in gen 1 the DC-DC (which downconverts 400v to 12v) and front HVJB ("High-Voltage Junction Box", which distributes HV in the front) are combined into one unit.

HVIL is the circuit which runs around the car using switches in various lids to detect tampering -- "High-Voltage InterLock". Evidently either the switch or connection to it in the DC-DC/HVJB is intermittent. Well this is a very minor problem but takes major effort to fix.

So instead of prying open the Gen 1 DC-DC/HVJB, or replacing it with another gen 1 (which they may not have), they want to upgrade the system to gen 2. I'm surprised they only want $3k for this. It would make the car more reliable in future though.

I'm sure that when they had the car they removed and reconnected the low-voltage connector to the DC-DC (which carries HVIL). This would re-seat the connections, and could have been the only problem.


FoxSTL2HOU: Your Battery Management System had experienced a failure. (f) And the Gateway predictably, threw a warning. (w) Without more internal codes there's no telling.
 

Zuikkis

Member
Aug 19, 2020
247
287
Finland
I'm having exactly the same kind of problem!

I already started a new thread:
Model S dead, "Vehicle may not restart"

But can anyone in this topic confirm what the actual cause was?

I'm suspecting it's just the 12V battery, because it has been charging with a 10Amp C-Tek "smart charger" for 3 hours now and still only showing 12.5V.. Should be way over 14V while charging.

Or obviosly could be that the onboard DC/DC-converter is broken, which then again caused the battery to drain..
 
  • Like
Reactions: Merle

Merle

Member
Apr 5, 2019
156
126
Tahoe
I'd posit it's the battery too. If you don't get the error while it's on the charger ...

Anyway, I popped off the nosecone and checked the 12V battery from the two poles behind the nosecone (hooray for pre-refresh) - it showed 11.4 volts if I remember correctly. I popped on my 12V charger and the screens immediately popped back up. I let it charge overnight (both on the 12V charger and plugged into the the EVSE) and the error messages did not return. I checked the battery each morning for the next couple of mornings and it was consistently around 12.6V after sitting overnight w/o being driven...lower than I might like, but it seemed ok.

Then I'd buy another battery.

I'm suspecting it's just the 12V battery, because it has been charging with a 10Amp C-Tek "smart charger" for 3 hours now and still only showing 12.5V.. Should be way over 14V while charging.

That's how it works. You apply a higher voltage to the battery and it'll charge. The 10A is only how quickly you can charge, presuming you can charge. If you have 1000A but a charger capable of pushing 11.5V ... you'll never be able to fully charge the battery.

Voltage > battery = charge
Amperage = speed of charge

That's why alternator and other systems (that are healthy) crank out 14V (give or take) and that's how we measure the health of a charging system (including alternator) to see if we're capable of meeting the needs of the system. Take out the alternator, and we'll see only battery voltage (which will drop while in use). Have no battery and leverage a 100A alternator, and we'll constantly see 14.3V (which is what we do when swapping batteries when not running to lose our radio settings in an older car).

Few more variables with LiPo batteries (e.g. motorcycles / dirt bikes) when charging, especially from drained, but the theory is pretty much the same.

I always think of it as a stream / river. If you have a near level surface (voltage difference), you'll never fill up the pond (battery) past a certain point. The amperage is how much water (electrons) are flowing to help fill that pond.
 

CCsayz

Member
Mar 9, 2020
5
1
Seaside Ca
I'm having exactly the same kind of problem!

I already started a new thread:
Model S dead, "Vehicle may not restart"

But can anyone in this topic confirm what the actual cause was?

I'm suspecting it's just the 12V battery, because it has been charging with a 10Amp C-Tek "smart charger" for 3 hours now and still only showing 12.5V.. Should be way over 14V while charging.

Or obviosly could be that the onboard DC/DC-converter is broken, which then again caused the battery to drain..
I just went through this with the SC. They told me to buy a new battery. I told them I replaced the battery in July (9 months) and then we got into a discussion about updating software etc. My Tesla became unresponsive due to low 12v. I attached a battery charger to the nose cone terminals and it came back. However my 12v system wasn't being recharged. I took it into the SC and they told me they couldn't help unless I updated the software. They then told me that the HVJC needed to be replaced $1000 + $195 diagnostic fee + Labor + additional parts. I declined since you can get a used HVJC from many sources and 3d party can replace for around $500 out the door vs $1500. The main.issue was my battery 12v not charging but there was some Hvil codes too. But since they updated the software and who knows what else the 12v has been working and not needed to be replaced. I didn't want to get into a chain of "let's replace this part and go down the line" since there's many reasons for a hvil error?! What happened with your?
 

CCsayz

Member
Mar 9, 2020
5
1
Seaside Ca
Hello All,

So a week or so ago, our 2013 P85 threw a slew of errors at home as we went to leave (i.e. Unable to Drive: Voltage supply too low; Electrical system power reduced: Vehicle may shut down unexpectedly; Power reduced: Vehicle systems shutting down; Vehicle may not restart: service is required). Shortly thereafter all of the screens went blank. Some sleuthing here on TMC revealed it was likely tied to the 12 volt system somehow. Anyway, I popped off the nosecone and checked the 12V battery from the two poles behind the nosecone (hooray for pre-refresh) - it showed 11.4 volts if I remember correctly. I popped on my 12V charger and the screens immediately popped back up. I let it charge overnight (both on the 12V charger and plugged into the the EVSE) and the error messages did not return. I checked the battery each morning for the next couple of mornings and it was consistently around 12.6V after sitting overnight w/o being driven...lower than I might like, but it seemed ok.

Anyway, I was able to drive it to the service center (no errors) and dropped it off. After a couple of days they indicated they wanted to replace the DC to DC converter (over $3k). The invoice explicitly indicates:

"Reviewed vehicle logs and found the HVIL to be intermittently open. Performed diagnosis of the HVIL circuit and found that the lid switch on the DCDC is intermittently open. Recommend replacement of the DCDC for the second generation retrofit as the first generation are no longer available."

After some additional research on the DC2DC converters here on TMC and elsewhere I see the fuse issue isn't uncommon, but in my case that doesn't sound like the issue (a fuse would be a lot more binary). I also see references to the "lid switch" on the HVJB, but I haven't seen any references to a lid switch on the DC2DC unit so my questions are:

  1. Basic Question - Is the "lid switch" referenced here just a simple magnetic reed type switch that is used to detect that the "lid" (i.e. case cover) is actually on/closed/sealed up? (i.e. the "fancy" version of what we've all seen on washing machine and dryer lids for years)?
  2. Is there a lid switch on the DC to DC Converter? - I haven't seen it listed or referred to in any schematics so I'm just not sure there is one (although it might make sense that there would be)?
  3. Any other ideas? I have seen at least one tech bulletin referencing the 4 or so connectors that actually connect to the DC to DC converter (hvac, heater, input, etc.) and even a TSB where there is a new harness for those connectors (essentially, sounds like the pins were a bit short in some cars). Maybe someone like @Ingineer will chime in (hint, hint).
I am picking up the car today (w/o them repairing it), while I research this further. Honestly, while I believe there could very well be an issue in the HVIL, I'm not 100% sure the DC to DC converter itself is the issue.

Thanks all and happy new year!

Anyway, m
I've been going through this same issue. They wanted to replace the 12v but I've already replaced it. So I also charged mine with a battery charger and the nose cone terminals. I take it to the SC because the HV system isn't charging the 12v. They say my software is out of date since I haven't updated for 9 months, that's another story. Anyway, they say that they need to replace the high voltage junction box. Somehow my 12v is now being charged by the HV system so I decline their recommendation since my initial problem is solved. However, I suspect that my HV battery heater is not functioning properly and that might be the cause of the issue or drive unit, DC-DC converter or?
 

cab

Active Member
Sep 5, 2013
1,033
721
Grapevine, TX
Sorry, I meant to come back to this thread. Ultimately, nothing. I picked up the car in mid-January (when I last posted) and it has been fine ever since...about 1000 miles worth of driving ago. I have been carting around jumper cables ever since, but so far, no need. We'll see if it crops up again next winter with "heating".
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top