RX400h

I have a friend who just bought one, a few months ago. His wife has a Range Rover but he didn't want to take that camping. Thus far, the only thing he dislikes about his LX is the fuel mileage. Other than that, he really loves his LX.

Has it been very hot out? I suspect that the rubber seals can get a bit sticky when very hot. Have you tried wiping a silicone lubricant on those gaskets?

There's a specific sequence of checks that should be done when a vehicle doesn't start. If you want to do your own repairs, having a factory owner's manual would be very helpful. The "Car Care nut" youtube channel can be helpful, also. The commentator is a Toyota mechanic who also works on Lexus vehicles.

Ideally, your vehicle would be on a lift so that you can walk around underneath and shake/inspect suspension or exhaust components. I've taken each of my vehicles to my favorite alignment/repair shop to investigate strange noises. At least twice, all they had to do is tighten up a bolt.

Some relevant info: P0763 Lexus: Code Meaning, Causes, Symptoms, & Tech Notes (engine-codes.com)

The first thing I'd do is call the service advisor to hear what he or she has to say about it.

At least one person claims to fix the issue by cleaning and lubricating the drive shaft splines. The Car wizard has some good advice and shows the undercarriage of a Toyota version (maybe not your issue but good advice, nonetheless) Another person replies with this statement:

Did you review your owner's manual?

Could this be the issue?

Are there any codes?

I don't recall ever seeing those, and I change the oil every year or so. I guess I wasn't looking for them, however.

That's a bit baffling, all right.

I cannot find anything that specifies the TCM's exact location. There are several sites (such as the one below) that offer remanufactured TCMs. Lexus TCM Repair Electronic Control Module Repair - Module Experts

Typically, you can do this by NOT stepping on the brake and then pushing the start button, two times. Push it again without stepping on the brake pedal and the radio will turn off.

I am a bit shocked that a load test was not done. How can anyone one for certain if the battery has enough cold cranking amps to start the car unless they do that test. Regarding ground, if you connect the end of the negative cable to a ground connection other than the opposite end of the cable, and set your multimeter to audible continuity, the display should read zeros and emit an audible sound. That would affirm that the cable is grounded.

Did the AAP person charge the battery and then perform a load test? Do you have a battery charger? Sometimes if you charge a battery and it does not accept the charge, it could have one or more dead cells, which means the battery needs to be replaced. However, if the battery can be charged to beyond 12 volts, and you can successfully start the car, then you should measure voltage while the engine is running. If the alternator is good, you should see over 13 volts. My car alternator outputs about 13.5 volts. Make sure that the battery cable clamps are pushed down all the way before they are tightened. The connector's inside diameter and post should be cleaned with a wire brush tool that is made for this purpose. Once each clamp is tightened, you should not be able to rotate it.

So you are referring to backlighting for the heater control panel? Is it for only the panel and nothing else? I assumed you looked in your owner's manual? Also, check the fuses if you haven't, already.

I assume you gave the overflow tank level and radiator a thorough look. I once parked over a piece of a cardboard box. When I started the car, the cardboard was sucked up against the radiator or its fan. Within a couple of blocks of driving, the temperature climbed quickly. I pulled over and quickly found the culprit.

Here's a generic instructional video: The instructor tends to repeat himself at times but the bulk of this video is very good.

Is there a way for you to check the fluid level? Has it ever been replaced?

Have you been experiencing more traffic? Lengthy periods of slow or no motion could do it.

Have you checked this section? Workshop Tutorials - Lexus How To Guides - Lexus Owners Club of North America

If this were a common problem, then perhaps drastic measures of change are required, but I have not noticed dozens forum members complaining about having this issue. Our RX has been bullet-proof for over 17 years.

You are correct. I suspect that the ambient temperature plays a role in how the engine's computer alters power output potential. So if you are driving under cold ambient temperature conditions, the performance difference among octane selections may be less obvious.

You are correct, the 2020 NX300h gets 33 MPG city and 30 MPG highway The 2022 NX350h gets 41 MPG city and 37 MPG highway. I'm not sure Lexus did this, but I believe the NX hybrid now requires premium fuel.