Last week I was cleaning my garage and parked the GX in my driveway overnight. The next day my TPMS light came on. It turned out to be my spare, it was low on air.

I aired it back up to 35 PSI and the TPMS light went off. To make sure I didn't have a slow leak I kept it the back cargo area. I checked the spare this morning and it still had 35 PSI. I had some family come over and I needed to use the 3rd row so I took the tire out and left it in my garage but the TMPS light never came on the entire day? Why would it come on if the spare is low on air but not come on if the spare is missing?

All of the posts I've found people were complaining about how to turn the light off not about why the light isn't coming on.

 

I looked up several different makes and they all seem to work differently. I also read on an Audi site that their system would not alarm as long as it saw at least 4 of the 5 tires.

I couldn't find anything on Lexus. Perhaps ours work like this?

Got this from another site.

It is based on Low Tire Pressure not Missing tires...

So you can take your spare off, the wheels do not send signals out at all unless a tire is sending out a low pressure signal... Some of the more advanced systems send out actual psi readings.

Just make sure you have AAA, You are going to need it when you get a flat 70 miles from nowhere and the spare is sitting in the garage.

 

I was thinking of that but when I removed my spare tire on my Tundra the TPMS light came on so I assumed it was the same for Lexus...maybe not though?


I have USAA road side but I'm definitely putting the spare back on. I just had the spare in the cargo area because it was easier to check the pressure if it was a slow leak.

Today was a spur of the moment type of deal and I needed to use the 3rd row and was in a hurry so I just put it in the garage. I have some Amsoil diff oil and I'm been meaning to change the diff oil but I've been too lazy. I guess I should change it this weekend since it's easier with the spare tire removed.




EDIT:

I still haven't put my spare back in. On the 19th, exactly a week after I started this thread, I started my GX to run errands and immediately my TPMS light starts flashing (malfunction) not solid (low tire pressure). I put my spare in the cargo and within 2 seconds the light turns off. That's weird it took a week for the system to noticed a sensor was missing?

 

I would be of the same mind. If it works that way on the Tundra, one would think it would be the same for the Lexus.

You always get to the solution so I'll be looking forward to your answer