Large parasitic draw on 12v system after windows left open in rain storm

[Dovetail]

Hi Everyone,

I have thoroughly enjoyed my 2012 leaf for the past 6 months. I was just thinking how little work I have had to do on it, when an unpredicted isolated thunderstorm dumped 1/2" of rain through the open front windows. When I got home, I turned it on and rolled up the windows with no trouble. The next day at work, I let it dry out in the sun with the windows open. When I came out at the end of the day I was greeted with a dead 12v battery. It started right up with a jump start and I drove home thinking nothing more of it. LeafSpy showed it charging the 12v battery properly. The next morning, dead 12v battery again. I checked the current draw with a clamp on ammeter at the negative battery terminal with the car off, doors closed and after waiting 10 minutes. It shows just under 3 amps of draw with everything off. This kills the 12v battery very quickly...

So far I have tried pulling fuses one at a time while checking the current draw at the battery. All test were done with the car off, and driver door open, but pillar switch pushed in. When I pulled fuse G,H,I from Fuse Box #2, the draw drops to about 1 amp. If I pull fuse #43 out of Fuse Box #1, it drops to about 0.1 amp. I also noticed that the M/C relay in the Relay Box is warm to the touch and seems to be active (clicks on when I place it in its socket. The same is true of the motor fan relay in fuse box #3.

Other than that, I unplugged both front window switch pods as recommended in another post (they both certainly took on water), with no change. I also removed the glovebox to look at the VCM since both relevant fuses seem to relate to it. It looks dry, and can't imagine it getting wet from that rain storm so far under the dash.

Does anyone have any thoughts? I am about ready to just install a disconnect on the negative cable and disconnect the battery whenever I park for more than a couple of hours.

 

[Stanton]

Not to state the obvious, but what makes you so sure that your 12v battery isn't "shot" and needs replacement? Once you "kill" a lead-acid, it doesn't necessarily bounce back. I don't know why some of the relays should be "warm to the touch" after disconnect/connect, but water can do strange things to electronics.

 

[Dovetail]

I guess I am not sure. It holds its voltage well overnight after charging and dissconnecting it from the car, but I'm sure it will be shot after this treatment even if it is not already. If the battery is no good, what would cause the car to draw current from it when it is turned off? If some of the electronics sense a low voltage do they not shut off for some reason?

I will try a known good battery and see what happens. That is certainly an easy test.

 

[Dovetail]

I tried another battery that I know is good, but still the same results. I made sure it was topped off with a separate charger first before installing it. After about 15 mintes with the car off and without disturbing any doors/windows, it was reading a voltage of 12.5 and a current draw of 2.24 amps. Any other ideas?

 

[goldbrick]

You can probably find a wiring diagram for your Leaf at nicoclub.com. I'd look through that and see what circuits are powered by the fuses and/or warm relay you mentioned in the OP and try to determine if they are malfunctioning somehow.

 

[knightmb]

I tried another battery that I know is good, but still the same results. I made sure it was topped off with a separate charger first before installing it. After about 15 mintes with the car off and without disturbing any doors/windows, it was reading a voltage of 12.5 and a current draw of 2.24 amps. Any other ideas?

That 28 watt power draw would kill any Leaf SLA after +13 hours of use given the SLA was brand new, fully charged when you started. I'm guessing that either you drive the Leaf often enough to not encounter a dead 12V battery or the mystery load must be stopping at some point? :?

 

[Dovetail]

That 28 watt power draw would kill any Leaf SLA after +13 hours of use given the SLA was brand new, fully charged when you started. I'm guessing that either you drive the Leaf often enough to not encounter a dead 12V battery or the mystery load must be stopping at some point? :?

At this point, I have to pull off the negative terminal if I am parking for more than a few hours, otherwise it will be flat at the end of the work day.

I have the factory service manual and have been looking through the wiring diagrams. One relay is the SSOFF (VCM Self Shutoff) relay. Its signal comes from the VCM, and its purpose is to turn off the VCM. Its switched line goes right back to the VCM. From the FSM-"VCM also activates the SSOFF relay so that it can shutoff VCM power when VCM stops (self shutoff)."

The second one is the M/C relay, which recieves its signal from the VCM, and is responsible for supplying power to each ECU in the VC system. So it seems that something is keeping the system from turning off. I don't know if that is a faulty sensor or switch that may have gotten damaged fromt the rain, of if that was just a coincidence.

I guess the next thing i can do is bench test the two relays, but after that I am not sure where to go.

 

[lorenfb]

That 28 watt power draw would kill any Leaf SLA after +13 hours of use given the SLA was brand new, fully charged when you started. I'm guessing that either you drive the Leaf often enough to not encounter a dead 12V battery or the mystery load must be stopping at some point? :?

At this point, I have to pull off the negative terminal if I am parking for more than a few hours, otherwise it will be flat at the end of the work day.

I have the factory service manual and have been looking through the wiring diagrams. One relay is the SSOFF (VCM Self Shutoff) relay. Its signal comes from the VCM, and its purpose is to turn off the VCM. Its switched line goes right back to the VCM. From the FSM-"VCM also activates the SSOFF relay so that it can shutoff VCM power when VCM stops (self shutoff)."

The second one is the M/C relay, which recieves its signal from the VCM, and is responsible for supplying power to each ECU in the VC system. So it seems that something is keeping the system from turning off. I don't know if that is a faulty sensor or switch that may have gotten damaged fromt the rain, of if that was just a coincidence.

I guess the next thing i can do is bench test the two relays, but after that I am not sure where to go.

Hopefully, it's not an ECU that got water damaged. It's not uncommon to have that occur on any vehicle whether a BEV
or an ICEV, after a very rainy season where a water ingress occurs. A water damaged ECU is typically not repairable,
and ECUs can be very costly.

 

[Dovetail]

Well I bench tested the two relays this evening, and both seem completely fine. Another thing I noticed is that when I plug in the bluetooth OBD adapter, LeafSpy is active no matter what the state of the car's ignition is. I guess that makes sense if all the varius ECUs are not shutting off. I don't think Leafspy used to work when the ignition was off. Is that correct?

 

[Dovetail]

By the way, here are the current DTCs read through LeafSpy:

C1A62 0108 BRAKE Control Mod Pwr Supply BR-53
B29A0 296C CHARGER N/CHG Port Engage Err VC- 95
B2802 2368 CHARGER Q/CHG Isolation Sig Err VC- 56
B2821 2328 CHARGER 12V Power Supply VC-65
U100A 876C CHARGER
B2902 4268 CHARGER OBC Memory Error VC-91

 

[knightmb]

I don't think Leafspy used to work when the ignition was off. Is that correct?

Correct, when the Leaf goes to sleep, everything is shutoff, LeafSpy loses access, etc.

 

[coulomb]

By the way, here are the current DTCs read through LeafSpy:
... 6 scary sounding DTCs...

I'm guessing that some of those could be due to the auxiliary battery voltage having been very low, and your frequent disconnection of the negative battery terminal.

Perhaps reset the DTCs (if possible), and use a battery tender instead of disconnecting the auxiliary battery, and see which DTCs persist, Do this for one or two days. If you can't use the battery tender at work, postpone this to the weekend.

B29A0 296C charger N/CHG Port Engage Err VC- 95
B2802 2368 charger Q/CHG Isolation Sig Err VC- 56

I wonder with the Leaf's propensity to waste power checking the J1772 charge port, whether these faults might be the cause. Water has far more effect on high voltage than on low voltage, unless there is acid involved. Leakage from (e.g.) the quick charge (CHAdeMO) HV wires to chassis would explain the second error above ("isolation"). Perhaps try some moisture displacement spray around the CHAdeMO port and its wiring.

Though I would have thought that a HV isolation fault would be enough to stop the car from driving. Maybe it can know that it's exclusively CHAdeMO related, so these are allowable as long as you don't attempt a CHAdeMO charge.

 

[lorenfb]

By the way, here are the current DTCs read through LeafSpy:
... 6 scary sounding DTCs...

I'm guessing that some of those could be due to the auxiliary battery voltage having been very low, and your frequent disconnection of the negative battery terminal.

Perhaps reset the DTCs (if possible), and use a battery tender instead of disconnecting the auxiliary battery, and see which DTCs persist, Do this for one or two days. If you can't use the battery tender at work, postpone this to the weekend.

B29A0 296C charger N/CHG Port Engage Err VC- 95
B2802 2368 charger Q/CHG Isolation Sig Err VC- 56

I wonder with the Leaf's propensity to waste power checking the J1772 charge port, whether these faults might be the cause. Water has far more effect on high voltage than on low voltage, unless there is acid involved. Leakage from (e.g.) the quick charge (CHAdeMO) HV wires to chassis would explain the second error above ("isolation"). Perhaps try some moisture displacement spray around the CHAdeMO port and its wiring.

Though I would have thought that a HV isolation fault would be enough to stop the car from driving. Maybe it can know that it's exclusively CHAdeMO related, so these are allowable as long as you don't attempt a CHAdeMO charge.

Yes, as it relates to extraneous current. The key issue with water is the circuit board corrosion and damaged circuit tracks.
Even more problematic is the moisture entering ICs and damaging the IC chips. Seriously doubt that Nissan specs Hi-Rel
military grade IC packaging (ceramic) for its ECUs. Water damaging ECUs is very common on many ICEVs, e.g. Audi, Porsche, BMW.
Water always finds a way in!

 

[Stanton]

I don't think Leafspy used to work when the ignition was off. Is that correct?

I believe that's a fact, so you may be on to something.

 

[LeftieBiker]

When you plug the dongle in with the car off, there is some activity, according to the lights on mine.

 

[GerryAZ]

There are some terminals of the OBDII port that are powered without the car being on, but LEAF Spy needs the CAN Bus communication to be active so it can read data from the various control modules. Therefore, the car must be on to get reliable information from LEAF Spy.

Enough systems will power up briefly when a door is open to allow LEAF Spy to connect, but the connection will drop as soon as some modules go to sleep when there is no activity. Even when LEAF Spy is connected without the car being on (when opening a door, for example), it does not display complete and accurate information because it cannot get data from modules that are not communicating.

The M/C relay (and perhaps the SSOFF relay) being energized is keeping the various modules powered which causes the excess current draw. You unplugged the window switches, but what about the other switches in the doors? Also, the keyless entry system has circuits in both front doors and the hatch that are active all the time. Those circuits might keep the VCM from sleeping and shutting down the relays.

 

[Dovetail]

The M/C relay (and perhaps the SSOFF relay) being energized is keeping the various modules powered which causes the excess current draw. You unplugged the window switches, but what about the other switches in the doors? Also, the keyless entry system has circuits in both front doors and the hatch that are active all the time. Those circuits might keep the VCM from sleeping and shutting down the relays.

I will give it a more thorough attempt. This weekend I will unplug all those switches again, and maybe even the parking brake and gear shift buttons (this was quite a violent rain storm- both seats and center consol were wet) to be sure.

Last night I put in a good 40 Ah SLA backup battery that I had, and cleared all the codes. I will take coulomb's reccomendation and keep it hooked up for a couple of days using a battery tender and see what happens. I also unplugged the 2G TCU for good measure since I was already under the dash and it is certainly not doing anything useful.

If these tests fail, would it be useful to monitor the CAN Bus messages? If so, can anyone point me towards a reasonable DIY way to read them? I haven't done my research on this yet. I'm guessing I would need a dealership to use their scan tool on it.

 

[Dovetail]

Two full days of a good battery, and disconnecting every plug in the doors and center console didn't result in any changes. I'm out of ideas at this point (Other than hooking a toggle switch up to the SSOFF relay to easily shut it down). I did purchase a salvage BCM for $75 on ebay. It seems like the most likely of the modules to fail. I hate throwing parts at a problem without knowing it is the problem, but we will see what happens when it arrives.

 

[knightmb]

Two full days of a good battery, and disconnecting every plug in the doors and center console didn't result in any changes. I'm out of ideas at this point (Other than hooking a toggle switch up to the SSOFF relay to easily shut it down). I did purchase a salvage BCM for $75 on ebay. It seems like the most likely of the modules to fail. I hate throwing parts at a problem without knowing it is the problem, but we will see what happens when it arrives.

Well, the only thing I would suggest is to start looking for simple issues. Maybe none of the modules or electronics is the issue. It might be some sort of short somewhere in the wiring between the positive and negative. Since the power draw is low, it's not enough to melt the wires but enough to be annoying.

 

[Dovetail]

Well, there is good news and bad news.

The used BCM arrived yesterday. I installed it this evening, and the car seems to go to sleep properly. The current is around 250 mA after a few minutes. The bad news is that I didn't realize that the key is programmed into the BCM, so it doesn't actually start up for a proper test. It just gives me the key is not detected symbol. I also didn't close the windows before swapping it, so it looks like I have to put the old one back in to get those windows up while I figure out how to program my key into the new BCM.

I think that's progress though!