In the past few days my 2020 RX350 had some random starting issue.

I get in the car, press brake and hit start. Dash lights up but it's not cranking. I keep trying, dash comes on and off a few times and then eventually after a few attempts it cranks and starts fine.

So far it happened twice in the past few days, both times at work after the car sat outside all day.
Just as a test I tried to park it on the driveway last night in subfreezing temperature thinking that it could be the cold weather but it started just fine at night and in the morning.

It doesn't look like a battery issue, I think that the key is also recognized because the dash goes into acc and on modes. What can it be?

 

I am not a mechanic, but I am thinking you need to get the car scanned for any codes. Hopefully, that will point you in the correct direction...

 

I would still check the battery.

I also have a 2020 and this is about the expected lifespan of batteries now days. Battery scanners are cheap or an auto parts place might be able to do it for free.

I checked mine about a month ago, and although it is working fine, it tested as weak. I used one of the Topdon testers....was like $25 or so on Amazon. Expecting to have to replace soon.

 

I'll test the battery but I think that if it starts eventually after a minute or two without needing a jump it shouldn't be a battery.

 

Maybe I'm wrong but it almost feels like it's not registering the brake press? Or at least it acts like this.

 

Well, based on an older traditional vehicle ...and I don't know what your RX uses.
You didn't mention how many miles are on the vehicle.
Not in any particular order:
Check Battery health and capacity (you mentioned cold temps in your region)(how old is your battery...if original, look here first especially if 3 yrs old)
check battery post connections, clean , re-seat
Starter solenoid -especially if high mileage or many short trips (many start engagements)
Starter relay
Neutral Safety switch
At this point, you may not be looking at an alternator issue, but...keeping it on the checklist ...

 

A battery might still start a vehicle intermittantly but be on the verge of failure. As I said, my battery is showing signs of failure but still (barely) passes some of the tests.

Three years is about the life expectancy of most modern batteries.

I would have it professionally checked first since it is the easiest fix. If it passes all tests then you can start looking for other issues. Just my 2 cents.

 

Some things to try: Have someone stand behind the vehicle while you step on the brake to make sure the brake lights come on consistently. This will verify the brake switch is good.
While in park, jiggle the gear shifter **** with your right hand while pushing in the starter button with your left. There could be a bad electrical connection there.
Try starting the car in neutral. The owner's manual shows how to shift to neutral with the engine off. Look under "driving procedures" in section 4.
Another possibility to consider is the starter push button switch. Although rare, it could be at fault since you mentioned you had to press it several times to get it to work.

 

Hi Stans - I'll bet you a beer it's the battery. Mine failed last month in my 2020 RX350 (32,800 miles). Alas, 3 years is about all you'll get from a battery these days. Have the dealer check it out because, if you are still under warranty, you can get a new one for free if yours tests bad :-)

 

Update: I stopped by the dealer. Had them scan the car and test the battery. Was told there are no codes and the battery "good but not fully charged" not sure what that means. I checked the volrage at home and it's 12.54v.
Changed the keyfob battery.
Tested the brake switch. It works good and the lightest touch on the pedal triggers it consistently.

I'm thinking about wiring a test light to the starter relay so if it happens again I can at least see if the starter received power or not.

 

"good but not fully charged", is a bit vague. Do you know if they did an actual "load-test" on the battery? Just a volt meter check won't do it. When you brought it to the dealer, did you drive it at least several miles before getting there? That should fully charge it, otherwise the battery is sounding suspicious to me.

 

I agree. Sounds really weird. They did a load test. The voltage reading was from my own voltmeter after I brought the car home. I'm planning to stop by autozone for another test.

 

at 3 years, your battery is on the chopping block.... yeah, a hundred or so dollars, Costco likely has one. Especially under frigid conditions, your battery is getting its share of work.... Me? I'd replace the battery . The other thing you can do if you dont want to spend on a battery, spend on a back up Lithium battery you can keep in your trunk or large glovebox. At least you can jump it from that. My brother got me one for Christmas a few years ago. I needed it for a V8 SC430 one day and I was surprised it did the trick. But, by the time you spend on that.....youre part way to a new 12v car battery.

 

it's really not about not spending the $100 for a new battery. I'm not trying to save money. Just trying to resolve a problem. At this point I just have no indication of a bad battery.
As for its lifespan - so far all my cars and bikes batteries lasted for about 8 years. Just last summer I replaced the original batteries in my 2015 lincoln and 2014 bike. At that point both still started and ran fine. The same hapenned in previous cars as well.

 

Then get a new battery, if it is not about $100.
This may be the solution, or if not, then one eliminated variable in your car’s current problem, which gets you closer to the resolution

from personal experience, I have Camry hybrid and it developed an issue with filling a tank with gas. It would kick out very frequently and took forever to fill. A change of 10 year old 12v battery solved this completely. $500 cad oem battery but cheaper than going to a dealership.
i had batteries last only 2 years too on Sienna. So battery mileage varies