jcesare
Well-known member
IMO this post on All Cars Electric.com comes close to explaining the problem Nissan is dealing with. The result is a massive hold until they actually figure it all out.
http://www.allcarselectric.com/blog/1058150_breaking-2011-nissan-leaf-start-failure--what-you-need-to-know/page-2
http://www.allcarselectric.com/blog/1058150_breaking-2011-nissan-leaf-start-failure--what-you-need-to-know/page-2
WopOnTour said:I disagree with some of the technical assessments made by this article and comments. The DTCs being reported by the affected Leaf owners are for "loss of isolation". Anyone working with or on hybrids or electric vehicles should be very familiar with these types of faults/failures. Essentially it indicates that select vehicle module/s have detected the presence of high-voltage (~300VDC of either + or - polarity)exists on the vehicle ground plane.
The threshold for these DTCs to "set" is somewhat variable but generally trigger when isolation is detected as being lass than 100-250K ohms. The high-voltage positive and negative circuits must remain isolated from the chassis and bodywork of a vehicle to both prevent damage to negative grounded compo entry AND maintain general electric vehicle safety.
This safety system then prevents the various components on the car from becoming "live" by actively disconnecting the energy storage system from its cabling to the rest of the car.
The air-conditioning system is always suspect with isolation DTCs are present due to the fact that the A/C compressor will often operate at high-voltages on many hybrids and EVs. Contamination, excessive moisture and/or air or the use of incorrect refrigerant oils (generally polyolefin ester based) can often trigger these DTCs. So in this case, one would think the use of the A/C compressor is merely the triggering mechanism, not necessarily the root cause.
Altering the software to lower the LOI detection levels to rectify this issue isn’t really a viable option UNLESS it is proven that there really isnt an LOI issue that exists and the threshold used by Nissan is abnormally high.
At this point I'm certain Nissan's efforts are focused on determining if there is truly an LOI issue present (and YES if so the safest thing to do is SHUT DOWN the high-voltage source via the contactor system)OR if an anomaly truly exists in their self-diagnostic routines for loss-of isolation.
Until such determination can be ascertained, it would not be advisable for owners of these cars to do anything but get these cars to their Nissan dealers where trained technicians can properly and safely assess if any risk exists.
No attempt to “clear” the DTCs or otherwise bypass these detected safety concerns should be made without full understanding of the risks involved.
HTH
WopOnTour