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

[bowthom]

Phil,
Excellent sleuthing, I suspect Nissan hesitates to lower the resistance / leakage test parameters due to safety concerns. I've been preheating in the AM (heater is on the "list" of offenders) without incident. The heater can draw 6 kWh and seems to me the A/C would be less so it has to be something other than just current draw. It is circuit sensitive, maybe noise, fly back, heat or current on that particular circuit that's knocking the IR detection out of range. Maybe all that circulating fluid through the pump and metal lines creates a static charge, add condensation and it finds it's way to the chassis then "POP" goes the P0AA6. Sounds like fun detective work doesn't it, I love a good challenge.

 

[mwalsh]

Phil - as usual, thanks for the highly informative posts. Why doesn't phpBB needs "Like" buttons like the other forum software.

Or even a thumbs-up icon! BTW....thumbs-up Phil!

 

[TomT]

Yep, that is what I did when mine shut down and it then reset and restarted. I have not had a shutdown since but I have also not pre-cooled since then either... I now am carrying a 10mm wrench with me as a precaution.

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

 

[Coffee_Slurry]

Is there any way to read these DTC values without a $Consult$ 3 or 4?

Can you fetch them over the ISO OBD Bus? Documented or standard CAN bus commands?

It would be great to have some poor-man's Consult software for an inexpensive USB-CAN adapter.

 

[TomT]

I suspect taking off both had nothing to do with it since once you break the circuit by removing one, the other has no affect. More likely, you did not leave it off long enough and removing the second bought you the time you needed. I left mine off for about 5 minutes when I successfully did it.

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?

 

[driveleaf]

Nice work guys!

As a strange follow up question, has anyone determined if their car will respond to a "request for update" from car wings once it's in lock down?

Just curious....

 

[LEAFguy]

Ingineer and others - thanks for your studies and your analysis. Very helpful!

This is, so far, a 33 page discussion. If I recall, most (all?) vehicles impacted have had the quick charge port. Could this have a bearing on the issue? Thanks.

 

[greenleaf]

Thanks for the tips. I am keeping a small wrench with the car in case I need to disconnect the negative terminal.

 

[Coffee_Slurry]

So I have to ask -- why the negative terminal?

 

[greenleaf]

So I have to ask -- why the negative terminal?

For safety reasons -- otherwise you might short circuit the positive terminal with a grounded part of the car.

 

[csriram45]

My car which was due 2 days back isn't delivered yet and my PD (BW Nissan) has no clue. I believe it was delayed due to an option that I had requested and with this AC Issue further. My VIN is close enough to the ones that seems to be affected so my assumption is that mine too is affected. No clue when it would get released but thats how it is so far....

Hopefully Nissan can atleast give a clear answer to the dealers so they can pass on the info to customers.

 

[Ingineer]

So I have to ask -- why the negative terminal?

So you don't accidentally form a "Ground Loop" from the body to the positive terminal with your metal wrench! :lol:

If you are wrenching on the negative and you hit some metal, it's already at ground potential and nothing bad happens.

-Phil

 

[Ingineer]

Phil,
Excellent sleuthing, I suspect Nissan hesitates to lower the resistance / leakage test parameters due to safety concerns. I've been preheating in the AM (heater is on the "list" of offenders) without incident. The heater can draw 6 kWh and seems to me the A/C would be less so it has to be something other than just current draw. It is circuit sensitive, maybe noise, fly back, heat or current on that particular circuit that's knocking the IR detection out of range. Maybe all that circulating fluid through the pump and metal lines creates a static charge, add condensation and it finds it's way to the chassis then "POP" goes the P0AA6. Sounds like fun detective work doesn't it, I love a good challenge.

They typically use a weak AC signal connected from the body alternately to HV+/HV- through a known resistance and read it's voltage. If the voltage is lower than a certain value the leak detection is triggered. The signal is read with an ADC input on a microcontroller, so the trip threshold is adjustable. This is how it's done in the Prius as well.

380k ohms seems awfully sensitive to me! That's only 1ma of leakage, worst-case! If it was me, I'd engineer it so it trips instantly at 100k or only if the fault exists for more than 10 seconds at 380k.

Because of this sensitivity, it may just be nuisance-tripping inside the A/C compressor.

-Phil

 

[garygid]

So, apparently there is not yet any actual firmware "fix" (to get around whatever is actually CAUSING the detection of an "apparent" problem)?

 

[GeekEV]

I met with a couple of Nissan engineers this morning to discuss my iPod issues. While they were here, I asked them about the AC issue. The main guy was hesitant to even talk about it (gotta love them lawyers) until AFTER he heard me describe the issue. Then he said that was a different department, but that he would make some phone calls and make sure they do whatever they could for my car while I had it in the shop anyway. So... Is there a fix yet (as some have suggested) or not? I dunno. If I find out anymore, I'll be sure to post it.

 

[davewill]

I met with a couple of Nissan engineers this morning to discuss my iPod issues. While they were here, I asked them about the AC issue. The main guy was hesitant to even talk about it (gotta love them lawyers) until AFTER he heard me describe the issue. Then he said that was a different department, but that he would make some phone calls and make sure they do whatever they could for my car while I had it in the shop anyway. So... Is there a fix yet (as some have suggested) or not? I dunno. If I find out anymore, I'll be sure to post it.

Kinda hard to blame lawyers for this one. An engineer working on the entertainment system probably doesn't have good info on the other systems... and probably should refrain from giving info he doesn't have.

 

[LakeLeaf]

Ingineer and others - thanks for your studies and your analysis. Very helpful!

This is, so far, a 33 page discussion. If I recall, most (all?) vehicles impacted have had the quick charge port. Could this have a bearing on the issue? Thanks.

Error codes are interesting beasts. They don't always give you a direct picture of what is going on. I had an issue with one of my vehicles which every few weeks would throw a few dozen error codes - and mostly the same error codes. The issue turned out to be faulty connectors on a wiring harness. Apparently, as the harness would move because of either car motion or car temperature it would throw a bunch of signals which were interpreted as certain error codes. There would be real error codes too, caused by the lack of communication over this harness.

So while very helpful, reading some error codes out of the on board computer doesn't always relieve the need for some solid brain work too.

 

[TomT]

Yep. The computer on one of my boats diesel engines starting throwing codes last year. Turned out that the problem was that the computer itself had a problem. I finally found it by swapping the computers between engines.

quote="LakeLeaf"]

Error codes are interesting beasts. They don't always give you a direct picture of what is going on. [/quote]

 

[GeekEV]

The engineer I spoke with earlier today called back to tell me my car was ready. I asked again about the AC issue and tried to get more info. All he knew (again, different department, I know) is that there WAS a firmware flash and they applied it. He didn't even indicate if the flash was to fix this issue, so I'm not sure if that means my car was affected too (Feb. delivery, vin 308), or if they just flashed it anyway. Make of it what you will.

 

[adric22]

The engineer I spoke with earlier today called back to tell me my car was ready. I asked again about the AC issue and tried to get more info. All he knew (again, different department, I know) is that there WAS a firmware flash and they applied it. He didn't even indicate if the flash was to fix this issue, so I'm not sure if that means my car was affected too (Feb. delivery, vin 308), or if they just flashed it anyway. Make of it what you will.

I found this thread interesting and I wanted to mention a possibility that I didn't see mentioned here. I work on the Prius a lot, which also has an electric-powered air conditioner. One problem that can occur is if a technician uses the wrong refrigerant. See, the Prius requires a special refrigerant that is non-conductive since the thing is driven by the main high-voltage battery and the windings are actually in contact with the refrigerant. Often an untrained tech will charge the AC system with standard refrigerant. Nothing will happen until the customer turns the AC on. At that point, it would cause a short in the HV system and the entire prius will shut down with every code imaginable and won't start back up. The only fix is to purge the system and recharge with the correct Toyota refrigerant.

I just wonder if maybe this was the cause and the Nissan Dealer hasn't had to deal with this type of thing yet and might not have realized what was happening.