2006 RX400h with about 230k

I don't own his car but helping a friend with this issue. He said he had issue with the car loosing power or just turning off while driving. I am not too familiar with the Lexus hybrid system but I scanned the car and P0A05 came up. It also has a check VSC and check hybrid system on the dash as an error. I did a little research and everything pointed to the invertor water pump not working or the fuse to it. The fused checked out to be fine. I checked the connections and cleaned it. I have a high level scan tool that is able to activate that water pump on my scan tool. When I turned it on, the coolant on the invertor pump started to move like it was being sucked or something. I put my hand on the pump and you can feel the pump action.

I am a garage mechanic, I've worked on mostly older honda/toyota/subaru but I am not too familiar with this. What other things should I look at or inspect?

 

Failed inverter pump is fairly common on this platform I would simply replace it. Can test okay but fail as you drive. You may also get code P0A93. Replacing this is easy enough only a couple of hoses, grab a jug of Toyota Super Long Life coolant and top off the reservoir. There is a bleed procedure but I find the system takes care of itself. Here is the pump.

https://parts.belllexusnorthscottsda...040-48080.html

 

Check starter battery if all else looks ok. had check hybrid and vsc warning lights that came on more and more regularly without explanation as everything checked and working. The starter battery appeared ok was starting ok but was 5 yrs and v slightly down on power…changed it and immediately faults came on less frequently and by end of a few days no faults and none since as if the system reset itself.

 

The regular 12v battery was replaced last year there is a 2023 sticker on it.

[​​​​QUOTE=789;11761910]Check starter battery if all else looks ok. had check hybrid and vsc warning lights that came on more and more regularly without explanation as everything checked and working. The starter battery appeared ok was starting ok but was 5 yrs and v slightly down on power…changed it and immediately faults came on less frequently and by end of a few days no faults and none since as if the system reset itself.[/QUOTE]

 

Yup had that pump fail early back at 90k miles, Now at 280k and running strong.

 

2008 RX400h FWD Tow Package, 188k.

Received P0A05 inverter pump code. Replaced pump with Denso G9040-48080 and blown fuse. Validated new pump runs using TechStream test. Cleared code. Upon Ready, code returns immediately and pump does not run. Per another thread's instruction, removed, cleaned, chased threads, and applied dielectric grease to the negative battery cable connection to the body, under the 12V battery support (it did not look suspicious, but never hurts to eliminate that possibility). Drove the vehicle for round trip 10 minutes, park 30, return 10 minutes in cool weather, to fully charge the 12V. No change, code persists.

It seems originally there may have been a difference in pumps for Tow Package and not. I could not find any currently available parts in Lexus that were different.

A seemingly unrelated issue, the car has a draw. If it sits for 3 days, the 12V is dead. I've gone thru a Walmart battery every year for 5 years. They finally stopped honoring the original warranty, so recently bought a new Optima Yellowtop, thinking that would solve it. Nope - dead in 4 days. I need to get a good multi-meter with a clamp ammeter and systematically pull relays and fuses.

I don't know what else to do. It seems to me that if TechStream can turn on the pump, that eliminates the possibility of cable and connector problems. All the data I see in TS looks normal, motor and inverter temp sensors, hybrid batteries blocks look surprisingly good. Any suggestions?

 

Do you have an amp clamp or a way to test parasitic draw?