Intermittent P0AA6 in 2011 Leaf

[w7gz]

I'm experiencing an intermittent P0AA6 HV leak detected code about once every 20 or 25 times I start my 70K-mile Leaf. It doesn't keep me from running my daily driver, but it is annoying to have to reset the code to be able to drive the car when it randomly appears.

Service writer at the dealer is extremely unhelpful: You have to have an appointment for a diagnosis, so you can't just drive in when the code is on. It's highly unlikely the code will be on when my appointment time arrives, and the code has to be on for them to do anything. So I'm faced with driving it onto the dealer's lot when the code appears, then making an appointment for a diagnosis 2 or 3 weeks in the future, and leaving it. Geez.

My question is: Does the Nissan CONSULT tool provide any additional information to narrow down the fault to any of the 7 or so systems that can generate it? Is there any point to me paying them $150+ to tell me there's a random HV leak somewhere?

What I've done so far:
1) After the code started to appear, I replaced the HV pack last week with an 11-bar known good one. Sadly, I still get the code randomly, but at least now I have the car's range and regeneration ability restored to factory almost-new.

2) While the car was up on jacks, I carefully went through it looking for packrat chews on all the orange cables and no damage was found, although not every inch of every orange cable is visible, of course.

3) In the old pack, I had to replace the precharge resistor, which was burned out because water had entered the HV connector to the battery, sending the car to auction. I've owned and driven the car here in the desert for almost a year without the isolation fault until now, so any water in the cable is long gone, and I didn't find any corrosion in the connector.

My next thought was to unplug the harness to the AC compressor and the PTC heater to remove 2 more variables, but I'm uncertain if that would immobilize the car.

What else could be the most likely cause of a very intermittent HV leak?

 

[nlspace]

That's a good idea to disconnect the A/C and PTC heater at the devices. If you disconnect at the HV DC/DC Junction Box then it will immobilize the car due to the series daisy-chain interlock loop in the HV connectors of the junction box.

Intermittent issues are usually connector problems so it might be a good idea to demate all the HV connectors that you can access to inspect the contacts for corrosion and clean if necessary before mating. It's really difficult to reach the backside of the HV junction box, but all the HV loads get their power thru that box.

Does this DTC show up when charging, or just when trying to start the car to drive?

The insulation resistance sensing is done by the LBC in the pack, so the problem is external to the pack.

Have you had any A/C repairs done on the car, maybe re-charged it with a non-spec freon?

Can you start with climate control OFF? Can you cause the fault by starting with climate control ON, with A/C ON and PTC OFF; then with PTC ON and A/C OFF? Try to isolate what mode causes the DTC.

 

[w7gz]

Thanks for the advice, I will try to disconnect those units and post a reply with findings.

So far, the fault only has occurred at vehicle start, not during charging. I almost never use the AC (even when over 100 degrees) and climate control is always off when starting the car. I doubt that any service has been done to the AC because the car came from a colder climate. I've owned Leafs for 10 years, and none of them has ever required AC service.

I will try the different starting conditions you recommended to see if I can reliably cause the fault.