Our 2013 450h with 123k miles had the oil cooler in the left front replaced due to a low impact fender bender in our driveway.

No problem for 2 weeks until we drove @ 65 MPH for 30 minutes and "hybrid system overheat" light came on for 10 minutes. We slowed to 55MPH and it went away. We had it towed to original repair shop who could find "no problem." My wife then drove it to solicit the problem and @ 65-70MPH for 32 minutes the "hybrid system overheat" light came on, but this time she lost power completely. We towed it to a Lexus dealer and they say the fan works, there is coolant, and they can't find the problem then wanted to sell us a new car! Help!!

Do I have to take a technician with me with a diagnostic scanner to scan it while the "hybrid system overheat" light is on? Doesn't it seem that the replaced oil cooler in the left front would be somehow related. The 450h has an oil cooler because it has a towing package. What is the path forward to make the diagnosis?

Thanks,
DML

 

Preamble: I am not sure what the problem is being reported, read on if you are desperate and looking for suggestions.

There are two different things that go on in hybrid vehicles and I am not sure which is being reported.

1. Cooling of the high voltage battery, cooling of the inverter. Essentially the electrical part of the hybrid.
You can start by making sure the rear seat foot well is clear of any obstruction and even open up the vents that are the heel level and make sure the passages are clean [essential preventative operation for your hybrid ... may not be listed in the manual].
Next is to check the coolant for the inverter ... there is peek window in the engine cover. There is a pump to circulate that coolant and some have reported problems with the pump. I assume the dealer has verified its operation.

2. Drive train. This as you reported was recently worked on. Any issue with the drive train can impact operating temperature of the hybrid motors. It can be a bad connector or connector not connected properly. Or even the drive train reaching temperatures out of its norm.

I would start with a visual check. Next would be to have a live monitor of your RX sensors. This requires advanced readers and a person with the know how of how to use and interpret the readings. Dealership should be able to do this for you but you have to agree to diagnosis fee [labor rates] with the possibility that they may not be able to reproduce. If you have time you can ask that you will pay for the diagnosis fee and drive around to reproduce [Do couple of test runs around the dealership ... that is how you will drive with the tech on board].

Salim

PS: Surprising part for me is that the hybrid part should be less stressed when doing 65mph +. It is at slow speeds that the hybrid is stressed both ways in generation and recovery.

You may like to investigate in the air flow of the front of the engine [very unlikely but should be part of the visual]

 

You need to pull the codes. It would be stored in memory. Can be done with a $10 adapter and a free app on your phone.