Unable to Restart after using AC (was AC causes failure)

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I talked to CS this morning and got a very different answer despite also speaking to a supervisor.
I was told that they are aware of the problem but have NOT yet been given a list of which VINs are affected, nor could they tell me if my car was one of them... They indicated that they should know by mid next week.
MY PD is also working on getting a definitive answer for me.


palmermd said:
sdbonez said:
He went away for a bit and just came back and confirmed to me that yes my VIN #728 IS impacted.

Next time be sure to ask him for the entire list of effected VIN's. Thanks for the update.
 
Yes, it would appear that the VCM is falsely sensing that the A/C compressor has an electrical leak to ground. One wonders how reducing the refrigerant level would have any affect on this... Perhaps if the compressor draws more than a programmed amount of power the system just ASSUMES that the extra power is going to ground and shuts down. Thus, reducing the coolant reduces the compressor load and the power drawn. Since there is no way for the VCM to monitor the amount of power drawn versus the amount returned as a GFI does (which should be equal in the absence of an electrical leak), this is the only data with which it can deduce an electrical leak in the compressor. Bottom line is still that it appears to be a software bug.

bowthom said:
P0AA6 HIGH VOLTAGE SYSTEM ISOLATION
Description INFOID:0000000006977190
Li-ion battery is equipped with the IR (Insulation resistance) sensing system. VCM receives the IR sensor signal
sent from Li-ion battery controller and monitors the insulation resistance of the high voltage circuit.
DTC Logic INFOID:0000000006977191
P0AA6
HYBRID BATT VOLT SYS ISOLATION
(High voltage circuit insulation is low)
VCM detects a insulation resistance calculated
based on IR sensor signal sent from Li-ion battery is 380 kW or less.
• High voltage harness or connectors
• Electric compressor
• PTC elements heater

• Traction motor
• On-board charger
• Li-ion battery
• DC/DC J/B
 
bowthom said:
Must be a typo "3127" below, no such DTC exists in the manual.

You're so right Bowthom...sorry it took me so long to get back to this. The second DTC was P31E7. You have also inspired me to download the service manual. Thanks!
 
mogur said:
Yes, it would appear that the VCM is falsely sensing that the A/C compressor has an electrical leak to ground. One wonders how reducing the refrigerant level would have any affect on this... Perhaps if the compressor draws more than a programmed amount of power the system just ASSUMES that the extra power is going to ground and shuts down.
What does VCM stand for?
 
LindaK said:
bowthom said:
Must be a typo "3127" below, no such DTC exists in the manual.

You're so right Bowthom...sorry it took me so long to get back to this. The second DTC was P31E7. You have also inspired me to download the service manual. Thanks!

Where do we download the service manual?
 
AmarilloLeaf said:
LindaK said:
bowthom said:
Must be a typo "3127" below, no such DTC exists in the manual.

You're so right Bowthom...sorry it took me so long to get back to this. The second DTC was P31E7. You have also inspired me to download the service manual. Thanks!

Where do we download the service manual?

http://www.leafic.com/wiki/index.php/Service_Manual
 
The Announcements section at the top of each subforum has a sticky called Reference Documents which contains links to many documents, including the service guide...
 
Hello,
My thought is: The IR sensor is at the battery pack and it can easily detect the return current so GFI only needs a stable ground reference. The VCM (vehicle control module) must also have a stable ground reference but the two grounds cannot be tied. The control electronics are on the aux battery and use the chassis. They must be isolated from the HV traction battery and all parts driven by it. Their only link is the DC to DC converter where power is provided to the VCM and acc. Those two grounds untied yet dependent on each other. When high current causes one, the other or both grounds to drift, the VCM sees this as leakage because the GFI ground is no longer centered between the forward and return current sense.
 
Perhaps so, but then it would have no way to differentiate what the source of the leakage was. Then again, maybe it doesn't care but if such was the case, why would the A/C compressor (nee "over charge") be singled out as the culprit and cause a fail-safe trip? Back to the service manual I go!


bowthom said:
Hello,
My thought is: The IR sensor is at the battery pack and it can easily detect the return current so GFI only needs a stable ground reference. The VCM (vehicle control module) must also have a stable ground reference but the two grounds cannot be tied. The control electronics are on the aux battery and use the chassis. They must be isolated from the HV traction battery and all parts driven by it. Their only link is the DC to DC converter where power is provided to the VCM and acc. Those two grounds untied yet dependent on each other. When high current causes one, the other or both grounds to drift, the VCM sees this as leakage because the GFI ground is no longer centered between the forward and return current sense.
 
Hello,
This is where the traces become important inside the driver module. If under heavy current the ground begins to drift and/or noise is induced or EMF coming out of the motor becomes a factor or,or,or. All it takes is for there to become a differential between the sensor ground at the pack and chassis. Or even a perceived one. The code is set when the leakage is detected and can be any of the listed sources, it does not differentiate between them. Seems to me each powered unit should have it's own sensor.
 
It's curious to me that the alarm still allows you to continue driving, but won't allow you to restart if you power it off. Is that the stated proper behavior for such a leakage alarm? I was told by a LEAF tech that an alarm, such as the battery overheating, will result in the vehicle immediately shutting down.
 
First off, let me appeal to everyone: If you ever have your car taken to the Dealer for service because your car is disabled or you have a warning light, please DEMAND they give you the DTC's (Diagnostic Trouble Codes) that their dealer computer system provides (Consult III+). This tells the true picture, and armed with this information it's difficult for anyone to B/S you about the true causes.

The DTC's I have seen involved in this issue are:

P31E7 - RESTART INHIBITION - Doing READY again is prohibited. Phil's Cause: Another fault has set this code to prevent battery main contactor from closing again because of possible danger. The car will NOT restart once shut down as long as this DTC exists! Disconnection of the negative terminal of the 12v battery for a few minutes will clear this code which will allow restart.

P0AA6 - HYBRID BATT VOLT SYS ISOLATION - Nissan's Cause: (corrected due to typos) VCM detects insulation resistance to ground (body) is less than 380k ohms. Fault in High voltage harness or connectors, Electric A/C compressor, PTC heater, Traction motor, On-board charger, Li-ion battery, DC/DC converter. Phil's Cause: This DTC means current is flowing from somewhere in the High-Voltage DC system to the Leaf's body. There is no way for the Leaf to determine where this fault is! This will always trigger a P31E7 (above), and the car will NOT restart once shut down!

B2840 - ON BOARD CHARGER - On board charger Malfunction - Nissan's Cause: (summarized) Input and/or Output voltage and/or Current (or ripple) over/under, Charger Temp too high, or internal charger component fauilure/fault. Phil's Fault: If you have excessive voltage drop (possibly due to extension cord use) or inadequate electrical supply, you could see this. Also: if charge is unexpectedly terminated, such as by a P0AA6, you could see this set.

P3173 - ON BOARD CHARGER SYSTEM - VCM detects an error signal that is received from on board charger via CAN communication. Nissan's Cause: Traction motor inverter. Phil's Cause: This comes if B2840 (above) is detected while charging. This could show up if you are plugged in and anything that could set P31E7 (above) is detected.

-Phil
 
Note that nobody that I've seen so far has reported ANY codes that pertain to the A/C system!

Since the A/C system is highly likely to generate an isolation fault (oil and refrigerant directly pass over the compressor motor windings), I suspect someone at Nissan is assuming this is likely and surmising that this could be caused by overcharge. (I seriously doubt this)

Sounds like the software "fix" is to simply raise the leakage current detection threshold to some higher value before the car will generate a P0AA6 DTC. (The service manual seems to imply that 380,000 ohms or lower will set a P0AA6, which is quite sensitive!)

-Phil
 
Phil - as usual, thanks for the highly informative posts. :) Why doesn't phpBB needs "Like" buttons like the other forum software. :)
 
FYI: You CAN reset this by pulling your negative 12v battery cable for a few minutes. It might also be a good idea to attempt to "honk your horn" once the cable is unhooked to help bleed off any residual charge in the various capacitors.

Until there is an official fix for this, try to get in the habit of checking for any warning lights before you power down. This way if you find one lit, you can simply leave the car on and not have to bother disconnecting the battery to get the car to enable again.

I'd say the best thing to do is drive it to a dealer at your earliest convenience. It will not harm anything to do so!

-Phil
 
I got stuck 80 miles form my house in Healdsberg as I had a second episode of non-starting. I was parked and used the pre-cool and when I came to the car the car would not start. Luckily I was able to get the car started, I first took off the negative 12V terminal which did not work and then I took both off and was able to get the car to start again, if stranded I recommend leaving the head lights on and then taking the neg terminal off and then reconnecting after a minute or so. If this had not worked I would have been in a bad situation. I plan to take the car to the dealer next week, perhaps it will break down there again as it did last week, is there a timer for that?
 
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