My Son Bought A Used 08 Lexus 450h GS With codes

Yes. In the "fail-safe chart" under Hybrid Vehicle Control in the repair manual (more info), the behavior for P0AA6 is shown as "normal driving*", where the * means continues to drive normally from detection of the code until you turn the car off, then no driving after that.

 

In the Gen 2 Prius, this code can usually be reset by disconnecting the 12v battery for a few moments. Once the code is reset, the car will again drive normally. If the code reappears, it will continue to allow you to drive normally until you turn the car off. Repeat as needed. Some people have done this for months.

I do not 100% know that the Lexus does the same, but odds are good it will. You'll need to verify if those P0AA6 subcodes on a Lexus means the P0AA6 is being caused by the battery.

Block voltages are identical to the Gen 2 prius, so the individual battery modules are identical, but iirc, the Lexus has 34 (instead of the 28 in a prius). This is good, because if you decide to repair the battery yourself, any Gen 2 or 3 Prius module will fit perfectly. You would just need to determine which (or if) modules are causing the problem.

 

That's on the low side. It gets charged from the hybrid battery, so could be a symptom of the issue, but 12v batteries going bad can trigger unrelated error codes. Any idea how old that battery is?

 

I think I was wrong, the GS450H may actually have 40 modules. I'm pretty sure it's a 288v nominal battery and uses the 7.2v 6 cell module identical to the Gen 2 Prius. The SUV models use a 9.6v module. But, I may be wrong. It happens sometimes. I haven't had opportunity to work on the Lexus models other than ripping out a battery now and then.

 

11.99 volts on a nominal 12 volt power system is not going to be the cause of any of the codes you have.

If you look in the repair manual (more info), you will often see troubleshooting workups that start with a quick check that the battery is over 11 volts, or to give it a charge before proceeding. Of course that doesn't mean it will start being the cause of any codes at 10.99 either; generally around 9 to 9.5 volts is where some of the car's ECUs will begin logging specific codes that mean "say, have you noticed the voltage kinda low around here?" Which of course are not spurious or unrelated codes, but mean exactly what they say.

But an 11.99 volt reading should be no distraction at all from just paying attention to what trouble codes you have been given and what those codes mean.

 

There is a company at drprius.com that works on hybrid batteries in your area. I can't vouch for them but it might be worth it to check them out. I believe they "recondition" hybrid batteries which is risky but any fix for a Lexus hybrid battery under $3k is risky.

 

Nice ride you got here.
The two codes you got, could be as a result of either of the codes triggering another.

The p0aa6, with the subcodes 612/526, points to the hybrid pack vicinity. Is there by chance if this vehicle was gotten, or has had a history of going through some kind of flooded water or rainfall somewhere before the purchase?

The p0aa6 isolation fault you have currently, would make the car not start(READY), each time you attempt to start it, when the engine is off. But immediately the auxiliary battery is disconnected and reconnected, the car starts.

I'm thinking, you either have some or all your modules are leaking electrolyte to the body ground, where the ECU monitors the return frequencies as it sends that to the insulation of the high voltage system. Any failure in the insulation integrity, would trigger this code, and could also be why you're getting the p0a80 replace hybrid pack code too(or coincidentally, the pack is bad already).

But from your screenshots of the block voltages, those results are correct, and normal, for your vehicle (same with highlander hybrid, etc).

Here's what you should do:
1. Get access to the rear seats, and open up the battery pack cover, to see if there are ponds of water anywhere close to the battery smart unit, or the HV relays, and orange cables too.

2. If there are traces of ponds of water(probably from rainfall), then you got to trace where the water got in there from. Sometimes, from my experience, it gets access through the grommets of the doors and rear hatch.

3. Don't just go and start throwing money trying to replace the battery pack.

4. Solve the high voltage isolation problem first, and clear the codes, and see if the p0a80 would still reappear. If it appears, you already know that pack has some low capacities.

 

Nice ride you got here.
The two codes you got, could be as a result of either of the codes triggering another.

The p0aa6, with the subcodes 612/526, points to the hybrid pack vicinity. Is there by chance if this vehicle was gotten, or has had a history of going through some kind of flooded water or rainfall somewhere before the purchase?

The p0aa6 isolation fault you have currently, would make the car not start(READY), each time you attempt to start it, when the engine is off. But immediately the auxiliary battery is disconnected and reconnected, the car starts.

I'm thinking, you either have some or all your modules are leaking electrolyte to the body ground, where the ECU monitors the return frequencies as it sends that to the insulation of the high voltage system. Any failure in the insulation integrity, would trigger this code, and could also be why you're getting the p0a80 replace hybrid pack code too(or coincidentally, the pack is bad already).

But from your screenshots of the block voltages, those results are correct, and normal, for your vehicle (same with highlander hybrid, etc).

Here's what you should do:
1. Get access to the rear seats, and open up the battery pack cover, to see if there are ponds of water anywhere close to the battery smart unit, or the HV relays, and orange cables too.

2. If there are traces of ponds of water(probably from rainfall), then you got to trace where the water got in there from. Sometimes, from my experience, it gets access through the grommets of the doors and rear hatch.

3. Don't just go and start throwing money trying to replace the battery pack.

4. Solve the high voltage isolation problem first, and clear the codes, and see if the p0a80 would still reappear. If it appears, you already know that pack has some low capacities.

 

lkq is a national company that has salvage yards in many places. I've gotten used parts from them but not batteries. They are a reputable company. LKQonline.com lists hybrid batteries from wrecked 450h for $1600 to $2000 that can be shipped. I believe they guarantee the batteries to work but don't guarantee beyond installation.