Hey everyone,

I have a 2011 Nissan Altima Hybrid that shows a hybrid electric system light. If I shut my car off when that light appears, the car will turn on but not start. There is no sounds. I need to reset the 12v battery terminal and put it back on for it to start.

So far I have replaced the 12v battery, changed the brake switch, and cleaned the terminals decently. This problem started to happen right after I changed my front brakes and calipers. Sometimes when I reset the battery, the light will show pretty much right away as I am driving, or it'll take a day to show I'm while I'm driving. The car doesn't shake or make a noise or shut down on me. I currently have to change my 02 sensor but that has nothing to do with the no start. But, for awhile I would start my car and it would shake and make a knocking sound but then go away after a few seconds. not sure if that has anything to do with my current problem.

Some codes I got when they system wouldn't turn on is P0AA6, U0293, B2562, and B261E. I have no idea where to start and neither did the dealer when I brought it in. I'm thinking maybe a lose ground or something after I lifted the car up to do the brakes/calipers but where would I even begin to figure out where the problem could be?

Let me know what you guys think.

 

P0AA6 is a high voltage isolation fault. Once detected, the vehicle is disabled. Disconnecting the 12V will clear the codes.

The most common cause is a physical leak in the hybrid battery.

Other causes in order of likelihood:

1. Transaxle
2. A/C compressor
3. Inverter
4. HV harness

Go to this page:

https://hybridautomotive.com/install-cr1pnp/

Execute steps:
1-11
#12, removing only items 1, 2 and 4
16-21
23

Ignore the red circles and observe the yellow squares. These yellow squared indicate the main (+) and (-) connections from the battery:


In the lower one, you can actually see a metallic portion between the wire and the plastic connector. This exists for the upper connector as well. That metal portion is part of the circuit and can be probed.

You'll need a multimeter with at least a 200VDC setting. Higher is preferable. An auto-ranging one is fine if it can handle > 200VDC.

Probe inside ONE connector to touch the metal crimping the wire and touch the other connector to the battery case. Observe the display. If it reads 0V or an auto-ranging unit may bounce all over at low voltage (mV) levels, or if a voltage is indicated, BUT it counts down slowly, you're good. If it indicates a voltage and holds it with little movement, you have determined there is a leaking module, and it is the source of the P0AA6 and the non-start condition.

Repeat for the other connector.

If the results aren't conclusive, you need to disconnect the battery computer.

Conduct steps 22, 24-29 AND disconnect the large orange connector from the battery computer. This will eliminate the "countdown" effect. ANY measured voltage is an indication that the battery has leaked.

 

Resetting the 12v battery would have something to do with this? or could this be more computer related issue?

 

I already answered this question in the first line of my post.

I have accurately identified the source of your issue. You have a P0AA6 HV isolation fault. The car is detecting a high voltage path to ground when they should be isolated, and the car is disabling start. A 12V reset clears the code and allows start. It is possible the source of the P0AA6 damaged a related computer, and that will need to be addressed, but the P0AA6 is caused by one of the 5 reasons I listed - repeated below.

Causes in order of likelihood:

1. Physical leak in the hybrid battery
2. Transaxle
3. A/C compressor
4. Inverter
5. HV harness

 

I have the same or very similar issue with a 2009 Nissan Altima Hybrid

Everything seems to be working good but when I get the Hybrid warning light and I turn the car off, it won't restart unless I reset the 12V battery.

My problem started because my HV battery was having issues, I was frequently getting P0AC4 and P0A80 codes, I bought a used one from a wrecked Altima, cycled (discharge-charge) all 34 cells from that battery, and then did the same with my original HV battery - I then picked the best 34 out of the 68 cells and put one battery together. After this, the EV mode comes in a lot easier and lasts longer, I also noticed that the switch from EV to Gas is a lot smoother.

No P0AC4 and P0A80 codes so far, but I'm getting the hybrid warning light and when it does the car won't start without resetting the 12V battery. Just to clarify, it always comes on, a few miles after startup.

I don't have a good scanner for Nissan, I'm using OBD fusion with the 2009 NAH add on.

It shows codes B2605-00, B261E-00 and B2110-00 so we share the B261E issue, OBD fusion names this code "Fueltype mis configuration"

I took the battery off again and dismantled it, carefully reviewed and test each celI, battery harness connectors and wires, swapped the DC-DC converters for 12V and Electric Power steering just to make sure that wasn't the root cause. No change, still getting the red Hybrid warning light

I was suspecting an HV leak but wasn't sure how to test, so I will follow Keith's instructions (thanks) and try to determine if that is the issue.

I also suspect the BCM because of what I read here:
https://zinref.ru/avtomobili/Nissan/...NGLISH/867.htm

I was thinking the next step -after ruling out an HV leak - was to find someone with a proper scanner -preferably a consult- and confirm why the red warning light is coming up and go from there, but if someone knows of a not so expensive software/app/reader that will talk to Nissan's hybrid system please share.

 

P0AA6 is not readable by consumer grade code readers. Professional level reader required.

Exercise extreme caution. A leaking battery can shock you. If the pack is out of the car, simply remove all the bus bars and check voltage from each module terminal individually to the case (bottom screws must be in). If you measure a voltage between a module terminal and the case bottom, you have found the leaking module. There may be visual evidence of "wetting" between the base of the module and the case bottom at the screw end of the module or corrosion on the bottom mounting screw.

If you do not find a leaking module, you likely have a fault in another of the components listed.

 

Thanks Keith

The battery is in the car right now, but I got pretty good at getting it out and taking it apart.

I found a local guy online that would scan the Altima for $50, or at least that is what he advertised.
I'll follow your advice and check around the ecvt and inverter to look for any evidence of damage/leakage.

 

If it's still in the car, you can do the quick check at the safety plug rather than at the main leads I described earlier in the thread:

1. Remove the safety plug.
2. Remove the safety plug fuse cover
3. Install safety plug - do not engage slide lock
4. Set multimeter to 200VDC minimum and measure from one of the fuse bolts to the battery case or other body ground.
5. If you measure a voltage that holds, you have a battery leak.

Since the battery computer is in the circuit, a good battery will show voltage, but it will slowly bleed down. Very slow voltage drop is likely a sign of a leak, i.e., if the voltage drops 0.1V every few seconds, it's probably a leak.

Divide the measured voltage value by 8, and that's the approximate distance the leaking module is from where the safety plug attaches.

 

I'm getting 91V constant at the safety plug fuse
Unplugged from the vehicle harness and re-checked, still 91V

Removed the HV battery and checked off the car, still 91V
Took the battery apart and checked each cell, #27 -counting from safety plug- had 6.6V to the battery chassis.

Replaced that cell, re-assembled and checked each cell, some show 0.01V but I'm guessing that is ok

Re-installed on the car, took it for a spin and no more Hybrid warning light, all seems to be working correctly, except for my remote that I think needs new batteries.

Thanks for the advice Keith, it worked for me.

 

Note that modules with the 4th digit of "J" and "K" are far more likely to leak than others. Occasionally will see F-I leak as well, but J and K are far more common. 3rd digit of 7 or higher with a 4th digit of "I" are likely to leak almost as much as J or K.

Cycling cells with an RC charger increases their likelihood of leaking exponentially unless you know what you're doing. Additionally, you are far more likely to experience P3011 to P3027 errors with "cycled" modules.