d2legend

2010 RX450h with 85K miles, driver perfectly fine for around town trips. Hybrid Overheat message only appear when on long trip (over 40~50 miles trip) and on cruise control. Engine temp is normal, recently hybrid coolant pump replaced (very recent due to message come up twice). No code at all. When I get the engine in Ready Mode, I see the coolant flowing slowly in the reservoir (not as turbulent as most describe). Fan running when AC switch on. Any hint? I know the Prius has a recall to update the ECU to keep the inverter running cooler but did not see anything from Lexus. I am lost here. Already ensure nothing block the hybrid battery vents. Anything else that I missed?

vlad_a

You may want to scan for a specific error code. Carista app/device can do this for you. Dealer can as well.
I had an MG1 overheat error, code P0A2D. Techs found and fixed a sensor wire that was broken. I had a loaner for 2 days.

Hybrid systems are warrantied for 8 years and 100K miles. Are you out of warranty already?
http://www.lexus.com/warranty

d2legend

There is no code when my mechanic use Techstream to scan it. About to bring in Lexus dealer, I think it is still in warranty.

F250

A 2010 with 80K is well within the 8-year 100K mile warranty window.

I'm watching this closely because I, too, have a 2010 450h with nearly 78K miles (not that I have the same problem... just watching to discover the solution to yours in case mine follows suit).

d2legend

Yes, I will report back to what dealer found.

d2legend

Forgot one detail: when I took the long trip and message appeared, I used cruise control. On the return trip (stay in SD for a few hours, turn on the car no message so I drove back), I did not used cruise control, no message at all. Any hint? Did cruise control cause the electric coolant pump go to sleep?

vlad_a

Cruise control does not do anything special, other than keeping steady pace, same as you would by pressing on the accelerator pedal.

d2legend

I know it should not but I have to ask.

rsutoratos

I never had that issue, 2010 w/127,800 miles. Let us know what they find...

d2legend

OK, got a call back from the dealer today, no code related, the tech only recommended doing "transmission service" (I assume it is replace the fluid), $210. I asked how the transmission related to the hybrid overheat and the service manager rambling oh it is related because it responsible for braking and recover the energy. Is it believable? I don't see how they are related. Since my car is out of normal warranty so I have to pay $150 "diagnostic fee" even if they could not find the issue. I ask can I apply $150 toward the transmission service, he said he will call me back.
BTW, he claim transmission service is required 8 years or 100K miles (coincident which is when my hybrid components out of warranty)

Droid13

The fluid in the PSD (aka transmission) would have to be in pretty poor condition (or missing) I think to cause an overheat. If such were actually the case, I would think another symptom would be terrible gas mileage, given the extra resistance causing the additional heat. That said, I think after 8 yrs and 100,000 miles a fluid replace is not a bad idea in any case.

I am pondering what measurement would occur that would generate an overheat message without generating a code. I know some of those smartphone apps / scan guages can also track specific coolant temperatures, well at least engine coolant, not sure about inverter coolant, but it might be worth a try to actually have something in the vehicle to monitor actual temps for when the message appears (if said fluid change doesn't help)

vlad_a

Sounds like they're fishing, hoping code wouldn't come back.
Do we even have a transmission, considering hybrid is a PSD device that works similar to a differential.

NVM, found it, page 953:

Clutchless

It is not really a transmission in the traditional sense, but it contains electric motors and other gear. It holds about 4 quarts of fluid and the fluid will wear out over time with depletion of additives. I think they are overcharging to change the fluid as it is a simple drain and fill like on a manual transmission. I have had 2 Lexus hybrids and have changed it on both. It takes about half an hour in my garage. I bet the dealer tech will be even faster = $150 profit on a charge of $210

d2legend

Clearly. The service manager told me when you see the code make sure you don't turn off the car and try to get the car to the dealer. I found that is BS, why would I risk the hybrid burn out to get to dealer if I am 40 to 50 miles away? May be I just run the dam hybrid until it burn out so I can the replacement under warranty? is that what they suggested?

d2legend

Absoutely, the only reason why I ask them to do it because I already out $150 "diagnostic fee", otherwise I am quite handy for those oil change. I always used OEM fluid when it come to tranny.
I actually did the tranny change when I bought the car at 80K so the fluid is like 5K (I change tranny fluid every 25K every auto car I have) so when the service manager told me "oh the fluid is very dark" I want to say BS to him but then I did not want him saying because I replace the fluid myself that void the warranty