GM Volt Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
4,384 Posts
Bummer. Wouldn't wish it on my worst enemy. Not a safety issue? There are plenty of places in LA where I would get pretty concerned if my car wouldn't start, LOL. I sympathize with the problem, but the spin doesn't help IMHO.
 

·
Premium Member
Joined
·
14,156 Posts
Yeah. I've heard about this. It seems there can be a problem if you use the AC and don't start the car. One guy experienced the problem at the dealer. He took delivery and was looking through the manual. It got warm so he turned on the AC. When he was ready to go the car wouldn't start. So to some extent it's an unusual situation and until they come up with a fix you can avoid it by simply starting the car before using the AC.

These things will happen. So far the Volt has been fairly problem free but bugs don't only show up on windshields. I agree the spin may not be the best but, on the other hand, it's not as if they're shipping thousands of cars and there seems to be a fairly simple workaround. No real safety issues so I don't see this as an unintended acceleration issue. People can be forgiving. Apple has done pretty well with the iPhone and it has a big antenna problem.
 

·
Registered
Joined
·
2,632 Posts
So far the Volt has been fairly problem free but bugs don't only show up on windshields.
As a non-sequitur, bugs don't show up much on a Volt's windshield either. While I suspect it was done to reduce wind noise over the wiper blades when they're parked, a side effect of the scooped hood is it forms an aerodynamic "ski jump" for bugs.

Most end up flying over the windshield, not into it. Sure, during her drive through the CA central valley my wife picked up *some*, but the nose was plastered. The windshield?

Not so much.
 

·
Registered
Joined
·
5,431 Posts
Nissan posted an ad where the Leaf will be exhibited locally at our largest shopping center in Puerto Rico this week. I haven't seen the Leaf yet, but do you believe I should print out that report and show it to the salespersons? Sometimes they don't know everything that is going on, and I know that this article can reduce potential sales.

Since we are in the tropics, almost everyone I know leaves the A/C on after turning off the ICE, such that it will turn on after the ICE is restarted so to cool the cabin as soon as possible (BTW, I leave the A/C off before starting my ICE). If this problem happened here in the Leaf, the buyers could return the vehicle back and complain until it was fixed, or demand a refund.

This isn't good for EV sales at all. So that is why the salespersons should know before trying to sell the Leaf. My recommendation to any salesperson is to use their products and be sure that they know beforehand about these potential problems, and know how to work around them.

Raymond
 

·
Registered
Joined
·
4,728 Posts
Based on the various threads I have read on ths issue, the A/C is really only the trigger mechanism but not actually the root cause of their problems. The DTCs that are setting are for "Loss of Isolation" of the high voltage supply. Having worked with these extensively they can be very problematic from a diagnosis perspective. Basically all of the high voltage components (including the electric A/C compressor) must maintain at least ~250K ohms of electrical "isolation" from the vehicle ground plane.So perhaps much like some of the Volt's, their diagnostic software was perhaps a bit aggressive in detecting these types isolation faults. If that is the case then a software revision and update process will be all that's necessary to remedy.

I seen lots of people on the the Leaf forum complaining that an A/C problem shouldn't cause the car to go into a "tow in" state, but ultimately an LOI must be considered very serious as the vehicle chassis could have potentially become "live" to either 300+ volts positive or 300- negative.
Not something to be messing with, shut'er down, tow'er in. Don't complain, it's for your own safety!

One aspect of the high-voltage A/C compessors that can potentially create this issue is either excessive moisture int he R134a refrigerant or incorrect oils (generally poly-olifin ester based) as both can create a a conductive pathway between the high voltage rail and the A/C compressor, lines, and other refrigerant carrying components (and as such the vehicle chassis/ground.)

Hopefully Nissan will quickly determine if they actually ARE creating a LOI issue or if they merely need to relax their LOI detection routines preventing these DTCs from triggering.
Unfortunate but really unexpected to run into these sorts of things on these ground-breaking cars.

A "tip-of-the hat" is appropriate to all you early adoperts!!
WopOnTour
 

·
Registered
Joined
·
1,684 Posts
This is but another operational defect which Nissan could have prevented had they been as serious about making the LEAF bulletproof as did GM with the Volt.

Simply inexcusable.

All the more reason to separate the two in any discussions - hey Jeff... please take note; in today's topic you group both together in a point you made towards the end of your post. The Volt does not need to cozy up with the LEAF, quite the contrary - the LEAF badly needs the Volt.

Let's let the LEAF gently fall to the ground on its own.
 

·
Premium Member
Joined
·
14,156 Posts
I remember when eBay had an outage and the world was ending -- the death knell for eBay. It managed to do OK. No doubt we'll see the same with the Leaf. While this is a HUGE PITA for the Leaf owners who have encountered the problem, overall it's not going to be a big deal. From reading the thread over at MyNissanLeaf it seems like it's a problem with the third iteration of the software. Not there in the first two, and it should be gone by the fourth.
 

·
Registered
Joined
·
4,728 Posts
I remember when eBay had an outage and the world was ending -- the death knell for eBay. It managed to do OK. No doubt we'll see the same with the Leaf. While this is a HUGE PITA for the Leaf owners who have encountered the problem, overall it's not going to be a big deal. From reading the thread over at MyNissanLeaf it seems like it's a problem with the third iteration of the software. Not there in the first two, and it should be gone by the fourth.
Personally, I am not confident that the root issue here is the software itself. Altering the software by merely lowering the threshold in which loss-of isolation faults are determined to be safe, isnt really a viable option. The owners of earlier cars not setting this LOI DTC may actually be driving an electrically unsafe car! So while these people are currently all smiles and giggles, they might in fact be only oblivious to the inherant risk that exists.

ANY significant loss of isolation between either of the high-voltage rails and the vehicle ground plane (say below 100K ohms) certainly MUST result in a disabled energy source, (i.e. tow job) or risk potentially damaged vehicle electronics. Another risk is safety of the user and/or technicians as this would mean a level of lost protection from a life-threatening energy discharge.Depending on the severity of the detected fault, traditionally this "disabling" occurs on the very next ignition cycle as observed in these current cases.

Propbably the WORST thing owners can do is to merely "reset" these DTCs using a scan tool or scanguage or by disconnecting the 12V battery. In fact while touching 12V battery negative they could very well be unknowingly putting themselves "live" to 300 volts posiitve (+) or negative (-) which on it's own isnt immediately dangerous, unless of course you find yourself simultaneously in direct proximity to the "opposite" pole.

You DO NOT want to become an active participant in a 300+ volt circuit!

WopOnTour
 

·
Registered
Joined
·
77 Posts
Probably the WORST thing owners can do is to merely "reset" these DTCs using a scan tool or Scanguage or by disconnecting the 12V battery. In fact while touching 12V battery negative they could very well be unknowingly putting themselves "live" to 300 volts positive (+) or negative (-) which on it's own isn't immediately dangerous, unless of course you find yourself simultaneously in direct proximity to the "opposite" pole.
Just like the Volt, the LEAF has a contactor that is opened to isolate the traction battery pack from the "under-the-hood" electronics when the vehicle is powered off to keep it safe when powered off.

The reason why clearing the DTC is the worst thing to do is that you affect Nissan's ability to properly troubleshoot and diagnose a problem.

To comment on the actual issue, I haven't had this problem in the 1,100 miles I've driven so far and I don't personally know any LEAF owners that have been affected. From the preliminary information gathered though, it appears to be a sensor set at too high of a sensitivity level. More information should be available in the next week or two.
 

·
Registered
Joined
·
4,728 Posts
Just like the Volt, the LEAF has a contactor that is opened to isolate the traction battery pack from the "under-the-hood" electronics when the vehicle is powered off to keep it safe when powered off.

The reason why clearing the DTC is the worst thing to do is that you affect Nissan's ability to properly troubleshoot and diagnose a problem.

To comment on the actual issue, I haven't had this problem in the 1,100 miles I've driven so far and I don't personally know any LEAF owners that have been affected. From the preliminary information gathered though, it appears to be a sensor set at too high of a sensitivity level. More information should be available in the next week or two.
No, I believe you misunderstood what I was saying and missed my point.
Trust me I am very familiar with DTC P0AA6 "Loss of Isolation" issues as these DTCs are somewhat generic- Toyota and GM uses them as well(or very similar) . In fact I've been very much immersed in this type of high risk diagnosis for many years now. Clearing these DTCs and Freeze Frame data files before a technician can properly read them with a scan tool is the least of your worries.

"The issue" is these very same DTCs are also used to detect "stuck closed" high voltage contactors. If a contactor is stuck closed, then it obviously cannot protect someone from getting "involved" in a high voltage scenario. The same goes for shorted cabling INSIDE the battery box BEFORE the contactors, exact same DTCs with no physical way to isolate via the contactors- a dangerous scenario.

So at this point there is no way to be 100% certain that a car with a P0AA6 has been set FALSELY (as many of you "suspect", but with to real evidence to support as such) OR
if there is truly an an isolation issue that exists (including sticking contactors). So you see there could very well be reasonable defects, even on a brand new car for the level isolation to be less than 200K ohms (the traditional threshold- Nissan could be more or only slightly less) Even a moisture contaminated refrigerant charge could technically result in this exact same DTC.

So if there actually WAS a contactor or cabling issue, then anyone handling the battery negative cable (or for that matter any grounded metallic surface on the car) they COULD actually be exposed to high level voltages without even knowing. Of course the risk would be even greater while the car was "ON" because at that point you KNOW the contactors are closed and the loss of isolation becomes a more serious issue. But clearly advising people to perform their own 12V battery disconnect to perform a "reset" (and therefore creating a low resistive bodily connection to vehicle ground plane) is certainly NOT the way to go.

Assuming no isolation fault exists despite it's detection is a serious breach of electrical vehicle safety protocols. The proper procedures would entail a trained technician wear the specified PPE (typically safety glasses and Class 0 gloves) and then measure for the presence of abnormal voltages at various cabling points following the manufacturers disabling procedures and using "live-dead-live" techniques throughout. This procedure alone will actually determine if a high voltage contactor is actually stuck, when a measured potential results as being much higher than anticipated.

Assuming this is just a case of "sensors set too high" (too low actually) is just plain irresponsible and dangerous
WopOnTour
 
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top