2022 Leaf with HV isolation fault code P0AA6 in The Bahamas with no dealer support

[GreaterInfinities]

Hello everyone, I have a 2022 Nissan Leaf that began having problems restarting after charging overnight. The charging would stop somewhere around 86% and then when I try to start, the EV Service Warning appears. I have a leaf spy and dongle and would see the P31E7 / P0AA6 EVC 157 DTCs which I know means an HV isolation problem which triggers restart inhibition (there is a > in front of the P31E7 but not in front of the P0AA6.) If I clear the codes, I can drive and everything is fine and normal until I have to charge it again. If I stop charging before it gets to 86% (this percentage varies a bit), I don't have a problem. We checked the HV battery voltage reading at the access opening on the floor of the back passenger section and there was a steady drop to zero showing no isolation problem. I've uploaded a sequence of videos. We live in The Bahamas and I imported my leaf second hand from the states at a dealer in Florida and we do not have a Nissan dealer that services EV or anyone else that I know of that will look at this for us. I would at least like to see if the problem is fixable and what our options are. Any information would be really appreciated. My biggest question is whether this is an actual HV battery isolation issue and how we can determine this if the reading from the access point looks normal. Are there other ways to check? I am concerned for safety since I keep clearing the codes and driving around. Thank you all.

 

[nlspace]

What is the age and condition of your 12V battery? An old, weak or worn out battery can cause a multitude of faults such as you have experienced.

Use your meter to check the open circuit voltage, then when the car is in ACC mode (press start without brake pedal), then when started to READY. Post the results.

Once you rule out the battery with a good strong fully charged battery, then you can troubleshoot the DTCs. But the ground fault isolation is tested from within the pack by the LBC, so not sure that your video test proves anything.

 

[GreaterInfinities]

What is the age and condition of your 12V battery? An old, weak or worn out battery can cause a multitude of faults such as you have experienced.

Use your meter to check the open circuit voltage, then when the car is in ACC mode (press start without brake pedal), then when started to READY. Post the results.

Once you rule out the battery with a good strong fully charged battery, then you can troubleshoot the DTCs. But the ground fault isolation is tested from within the pack by the LBC, so not sure that your video test proves anything.

The 12v battery was reading a little low but still over 12v. We charged it up anyway but it happened again so we replaced it. I can run that test to rule it out and will post results. The video I posted shows the same method shown in the link below 48 seconds in. Is this not the correct method for testing isolation leaks?

 

[cornbinder89]

Yes that will test for an internal pack HV leak to chassie. It is one place the HV can leak to chassie but not the only place it can leak.
At this point I think you are going to need help from someone with experience on the Leaf and EV's in general. I understand, you don't have a dealer on the islands, but may be there is some EV specialist?
Without knowing your tools and skill level, and the fact that HV DC is nothing to play around with, it is hard to recommend the next step.
Being on an island and "salt air" I would look at possible corrosion of connectors, but you must keep the safety protocols in mind.
Because the safety disconnect breaks the battery into two halves neither of which should be connected to the chassie, and the fact it only happens with a fully charged pack, did you test both sides and test when the pack was fully charged?

 

[BillAinCT]

Could there be a leak only on the wiring to the charger or battery? If the DTC is cleared does it return only at the next charge? The 86% level has to be a clue somehow

 

[cornbinder89]

The hard part is the intermittent nature of the fault. If it truely isn't present below the 86% and is above, it is going to be difficult in finding where the problem lies. As the above isolation test shows, there can be a slight voltage reading, that dissipates through the meter loading. If it is a very small leakage that can only trigger the code when the battery is near full charge, it will be difficult to isolate and find.
You may be reduced to continual clearing until the problem gets worse and easier to find

 

[GreaterInfinities]

Yes that will test for an internal pack HV leak to chassie. It is one place the HV can leak to chassie but not the only place it can leak.
At this point I think you are going to need help from someone with experience on the Leaf and EV's in general. I understand, you don't have a dealer on the islands, but may be there is some EV specialist?
Without knowing your tools and skill level, and the fact that HV DC is nothing to play around with, it is hard to recommend the next step.
Being on an island and "salt air" I would look at possible corrosion of connectors, but you must keep the safety protocols in mind.
Because the safety disconnect breaks the battery into two halves neither of which should be connected to the chassie, and the fact it only happens with a fully charged pack, did you test both sides and test when the pack was fully charged?

Thank you, that is a good point and I don't recall how charged up the pack was at the time of testing. I will get confirmation from my husband but he definitely checked two points in the access point so I believe that accounted for both sides. How can we check the other components connected to the HV Battery (AC and PDM)?

 

[GreaterInfinities]

The hard part is the intermittent nature of the fault. If it truely isn't present below the 86% and is above, it is going to be difficult in finding where the problem lies. As the above isolation test shows, there can be a slight voltage reading, that dissipates through the meter loading. If it is a very small leakage that can only trigger the code when the battery is near full charge, it will be difficult to isolate and find.
You may be reduced to continual clearing until the problem gets worse and easier to find

Thank you, I am anticipating it get worse unfortunately because the percentage keeps dropping. It started at 89%, then 86%, 85% and now fluctuates between low 80s and 85%. Are there other clues of leaky cells? Will leafspy show anything?

 

[nlspace]

Some notes about the EVC-157 video:
EVC-157 is a page number in the EVC section of the factory service manual and it changes for whatever model year of the car.

DTC P0AA6 is thrown for a reduction of resistance of the wiring insulation below 380k Ohms. Typical or expected values are on the order of 5 MegOhms, and the leakage current is ~10 to100 microamps. When the leakage current gets up to 1000 microamps it starts throwing codes. For example in a 2013 it is covered on pages 188-195, EVC-188.

A megohmmeter aka "megger" is the tool used in the FSM to determine if wiring insulation is leaking too much. The only use of a voltmeter is to determine if there is any voltage present on exposed HV connector terminals when disconnecting the A/C and Heater.

By his measurements the chassis was shown as being 337 VDC above the front pack and 72 above the rear pack because he had his positive test lead on chassis. He would have read a negative voltage with the leads in normal chassis (-) configuration. As it turns out this test worked for him because he had a direct short to chassis from a rear cell leaking electrolyte. But it does nothing to measure wire insulation resistance.



i suspect that his fault would not clear as the short was always present, so this may be a clue for troubleshooting in this forum thread since it has an intermittent nature to the DTC (clears and returns later).

A careful inspection of all the HV connectors might reveal corrosion that could be a leakage path. Warm moist air near the ocean can condense out onto cold surfaces leaving a salty residue that can conduct electricity; when the voltage is higher then the potential for some small current leakage is higher. Most intermittent faults are due to connector issues since a broken electrical component can't heal itself.

 

[cornbinder89]

A careful inspection of all the HV connectors might reveal corrosion that could be a leakage path. Warm moist air near the ocean can condense out onto cold surfaces leaving a salty residue that can conduct electricity; when the voltage is higher then the potential for some small current leakage is higher. Most intermittent faults are due to connector issues since a broken electrical component can't heal itself.

This is where I'd go, BUT and it is a very BIG BUT, you MUST understand the risks involved with dealing with HV DC and have the necessary safety gear to work with the voltages involved.
There is MUCH more risk dealing with 360-400 volt DC than 120 or even 240 volt AC. Poking around and not understanding the correct procedure and using correct safety equipment may lead to something posted on an electrical cabinet, "This can kill you and it will hurt the whole time until you are dead"!
DC will arc and not stop like AC will, it will also pass through you skin at lower voltages.

 

[coulomb]

The 86% level has to be a clue somehow

My wild guesses: the cells swell slightly with increased SoC?? That seems unlikely.

Another guess: some insulation is failing at a certain voltage threshold. Only when the cells get to a certain voltage does the insulation break down.

Yet another guess: a cell is leaking electrolyte. Weird things happen with chemicals and voltage.

Final guess: charging actually stops at 86% either because it's a DC fast charge or the battery is badly unbalanced, possibly due to the leakage. Just before the car disconnects the contactors, it does a leakage check, and finds it. This leakage could be in the charging circuit (wiring or electronics), or even the EVSE (AC "charger").

The only use of a voltmeter is to determine if there is any voltage present on exposed HV connector terminals when disconnecting the A/C and Heater.

IF the fault is present long enough to measure things (perhaps charge the car up to that ~86% point), then measuring the voltage from both sides of the mid-pack disconnect can be telling. I've seen a leakage found that way. One half measured a voltage that kept changing all the time, "swaying in the breeze". This was the good side. The other half measured a fixed voltage that was rock solid, not changing more than one Least Significant Digit. At that point (this was in a repair shop), they were able to drop the pack, measure the voltage at various cell interconnects to metalwork of the pack, and when it got to nearly zero, that should pinpoint the location of the leakage. I don't recall them ever getting back to me with the results, probably indicating that they found the issue without significant problem.

If the problem is intermittent, then this may not help. A megger might overcome any weak insulation, but it won't pinpoint the problem.

I'll repeat the warning already given: EV battery packs are very dangerous, and you need to know what you are doing, and use the appropriate safety equipment (1000 V certified gloves, totally insulated tools, multimeter rated to at least 600 V CAT IV, and so on).

Sadly, it might be best to consider replacing the whole pack. That's at least less dangerous than opening the pack.

Considering the possibility of salt water in the connectors, I agree with the earlier suggestion of carefully examining each battery connector for corrosion, and possibly just spraying with contact cleaner (not oil based, you want the kind that cleans but leaves no residue). Remove any obvious oxidation (e.g. green/blue powder, rust) by spraying and scraping.

 

[GreaterInfinities]

Could there be a leak only on the wiring to the charger or battery? If the DTC is cleared does it return only at the next charge? The 86% level has to be a clue somehow

I agree, there has to be a reason for that and I'm hoping we can troubleshoot without having to remove the battery pack which is why I'm reaching out to the community. If anyone has any experience checking for leaks in the wiring as you suggested, that would be very helpful.

 

[cornbinder89]

Well, if you have done the above test at the service disconnect between the seats, with the battery fully charged and don't see any leak there, you can check that off your list (at least for now) and move on to the connection at the front of the battery pack to the PDM over drive motor.
With the service disconnect out of the battery (battery disconnected) I would remove the connectors at the front of the battery box and clean with non-residue cleaner, while wearing protective gear. I would then move to the PDM and clean those connections before reinstalling the connector at the front of the battery (so will be dead when you are working on it, and will not require PPE)
None of this will 100% confirm where the problem is, but is the next likely area to look for it, and requires the least in special tools.
If all the connections are clean, no corrosion at the terminals and the problem still exists, then you are going to need a specialist. It is always possible the inside (internal battery box side) of the main power connector has some corrosion that is leaking to case, this would only show when the main contactors in the battery box are "pulled in" like when charging or running the car, so will not show in the 1st test you did. Working on energized 400 DC circuits is dangerous in the extreme, and not something I would attempt on "the bench" and most assuredly not in the car.
To find these kinds of problems is well beyond the scope of most, myself included.
Likely the best way to find the last problem is to remove the battery, open the case and inspect visually.
AGAIN, I will say 400 volts DC deserves a lot of respect and PPE to work on. Yeah, I get that you are on an island and can't get the car to a shop, but consider is it worth your life to try and solve the problem?
By design, the system is made to fail safe in all instances, so it makes it hard to diagnose a intermittent problem, when the system is in a "safe mode" the problem doesn't rear its head, and when it is dangerous to be working around is when the problem is detectable.
I would do the simple checks of the connectors, that can be done safely, then button it back up and see the problem is gone. It is about the best you can do, and most of the risk is mitigated with the service disconnect out when you are working on the cables to the front. A contactor CAN stick in the closed position, so don't assume everything is safe, but it would take multiple failures for the connector at the front of the pack to be live with the service disconnect out.

 

[MikeinPA]

GI, Do you have access to the repair manual? You can get the 2013 manuals here: https://ownersmanuals2.com/nissan/leaf-2013-repair-manual-ev-control-system-section-evc-43003 and https://ownersmanuals2.com/nissan/leaf-2013-repair-manual-ev-battery-system-section-evb-43004 I do not know where later manuals are available for free.

There is a whole section on diagnosing P0AA6 HIGH VOLTAGE SYSTEM ISOLATION , starting on page EVC-188 and going forward tp EVC-195. You will also need to follow some of the links into the evb manual. I skimmed it just now and there are multiple items to check before checking the main battery. In that you are not seeing voltage between the case and the terminals under the big plug--I would definitively start with Nissan's checklist for this on page EVC-188. I am guessing any competent mechanic could do most of this or even all of this except for opening the main battery. If you do work on this, you need gloves like this , proper clothing, and you need to read Nissan's documentation thoroughly. Their manuals for this vehicle are quite detailed and thorough, but topologically challenging. Also, if you work under this vehicle, wear safety glass and be certain the vehicle is secure. I prefer solid blocks under every wheel, like these: https://myliftstand.com/

 

[cornbinder89]

Theirs is a '22 model year so no free documentation, but I bet the '15 manual (Last free download on NICO's site) would be a closer match.

 

[cornbinder89]

A quick skim of the manual for 2015 shows a coupla 'operational" test to see what system generate the code. In other words, does running the A/C generate the code, does moving the car generate the code.
Because the A/C compressor is hermetically sealed scroll compressor, the correct oil and refrigerant is required to keep up the dielectric properties. Nothing special, but if someone added a "sealer" to the A/C system there might be unintended and very expensive consequences.

The Charging both on Chademo and the OBC should not generate the code because those systems have their own protections built into them, and if there is a fault will prevent the charge from taking place. That doesn't seam to be the problem here.
If the operational tests isolate the problem to one of the subsystems then they have you "Megger" that part of the wiring. Most individuals will not own a "megger" so that rules out much more indepth checks of the wiring, other than visual.
If I understand correctly, the code shows up once the car is charged beyond a SOC above 80% somewhere. If the code show before driving, and the climate control system is activated, then I think I would concentrate my efforts between the battery case and the PDM. By testing from the disconnect to chassie they have checked the cells and wiring as far as the main contactors. I believe the test show that there is no voltage leak at that point.
When you factor in what tools are likely available, and guess at the skill set of those doing the work. I would say there isn't much more than visual checks and cleaning of the HV cables and connections that can be done.
If going deeper, it will require more than most will have, so it almost is irrelevant what the procedure is if you don't have the equipment to carry them out.

 

[martinwinlow]

OP: On the basis that the best scheme for fault-finding is to eliminate the easy possibilities first, have you tried using a different chargepoint? I would borrow a portable EVSE (or even buy one - they are not expensive) and try using that for a week or so and see if the issue continues...
The other obvious thing that springs to mind is damage to wiring by rodents. My experience with EVs is mostly in dealing with Mitsubishi i-MiEVs but I expect the LEAF has broadly similar design architecture in which case removing the belly pan would be a first step. There are so many little nooks and crannies for little furry critters to nest in, much of it in close proximity to wiring looms. Remove the belly pan and any other accessible panels carefully so that you can see if there is any sign of rodent habitation eg chewed up bits of just about anything and droppings.

 

[MikeinPA]

As others have pointed out, this could be tiny amounts of current leaking around a connector, or rodents have compromised something enough to have the same effect. Both could involve trace amounts of salty moisture. Working on this theory, you could test this by opening the hood and applying sunlight to the engine bay to try and dry the wires out. Also, drop the first aero shield, inspect for moisture and fauna, then apply a fan for several hours during hot dry weather. If the % charge at which the fault occurs increases, then you have a diagnostic point.

Also, when troubleshooting an unfamiliar system, all too often there is more than one issue that needs to be identified and corrected. (edit) For example, the suggestion to try another EVSE is a good idea, in that the charge may be stopping due to one issue, and the P0AA6 fault coming from another issue.

 

[cornbinder89]

I don't think a different EVSE would make a difference, it is stated right in the service manual that the wiring from the charge port to the charger will not set those codes, and changing the EVSE will not change the charger or anything after the charger. The EVSE is just a glorified contactor and doesn't "set the charge voltage" only lets the charger know how many amps it is allowed to draw.
That said, it can't hurt if another is available, to give it a try. I wouldn't go out and buy one however.
Inspecting the wiring we all seam to agree is the next practical step, along with cleaning around the HV connectors. Both are doable with a few hand tools and some basic precautions taken.