FirstLexSC

This morning when I started my SC430 the tire pressure warning light stayed on. I then checked each tires pressure and found the front tires at 27.5 and the rear tires at 30.5. I drove to the local gas station and filled all tires to 35.5 and the warning light went off.

A couple of questions come to mind and I was wondering if anyone has experienced them of has any comments:

1) Are the tire pressure sensors fairly accurate. I thought I read somewhere that the light will not come on until the pressure goes below 26. My electronic gague could be off (its the Lexus electronic one - free gift)?

2) There was about a 10 degree temp change between yesterday and this morning. Has anyone experienced a a problem with the warning light when and as cooler temperatures arrive?

I will check the tire pressure for the next few days for a leak but I think the warning light was just a result of the tire pressure being lower than the recommended 33lbs.

FYI. I have a 03 SC430 with 4500 miles on it and the Dunlop Run Flats and love the car.

Thanks for your comments.

LXTACY

My pressure light comes on at that pressure also (between 27/28psi). Nothing to worry about, at least you know they're working

JCtx

Being a motorcyclist, I religiously keep my tire pressures at what they should be on all my vehicles (once a week).
I go with the recommended 33 all around on the SC; the RFs being hard as a rock already, no need to keep them higher. And yes, cooler temperatures will decrease your pressure at the tune of 1 PSI for every 10º. Check often until temps stabilize.
Remember our car has a 2-step warning: light first at around 28, as stated, and a light PLUS buzzer at around 20.

JC

Doc C

Mine came on a week or so ago. I have had all kinds of wheel/tire issues in the last few months, so I figured something was wrong with the sensor (went to sleep, came loose inside the tire again etc.) and took it to my dealer. They said that it was fine, I just had low tire pressure. The service tech said the sensors were very accurate and that they trust its reading more than they do a tire guage. Especially a cheapy tire guage like I've got. They gave me a shot of air (in my tire) and I was on my way. My pressure light also came on when I was chasing a T-Bird down the highway at 148 mph. It was 5 degrees outside. I heard that the sensor will come on if you go at a high speed for a prolonged period of time even if your tire is at normal pressure. My service tech said you need more pressure at higher speed and that's why the sensor functions that way. My two cents.

Doc C

JCtx

Doc, the manual says tire pressure should be 40 psi for speeds above 112 mph. This was obviously intended for the normal tires, but Lexus wasn't about to change ECM programming for cars fitted with RFs. Corvette recommends 30 psi all the time, and its top speed is in the 170 range.
When I finally can open this thing up (only 530 miles so far), pressure will stay at 33 psi. I only plan to top it out once, and not going over 112 after that, so I'll let the stupid buzzer sound. Important thing is you shouldn't worry about the buzzer if you're at high speeds on RFs.
As a final comment, the sensors on the vette (which has individual pressure readings for each tire) displayed exactly the same pressure as my Griot's Garage unit. This round unit (not digital) has 3 different heads with 0º, 45º and 90º; use the latter for motorcycles and the first for cars. It might seem a little inaccurate on light-warning systems like ours due to the programming logic to trigger alarms (eg wait for 'x' many inputs before triggering the alarm). This is also the case when you're rapidly accelerating, like on a top-speed run, so instead of 112, the warning might come on way above that.
Hey Doc, 148 is not too shabby; I'm proud of you . I'm curious if somebody has reached the top-speed limiter on this car. I'm sure I'll not reach it at this altitude; I'm guessing 140s at best.

Have a great weekend.

JC

Doc C

Yeah, I've never had mine above 115 since then. By the way, the Thunderbird was impressive. It was pulling right on up there. I broke off when run flat light came on. The light is the only thing that came on. I feel more comfortable with my Michelin Pilot Sports than the run flats. They make a huge difference at high speed. Actually any speed. As far as sensors go, I still think the way Lexus is doing the RX 330 and LS 430 is the better way to go. No sensors in the wheels. Uses ABS and VSC sensors to determine one wheel speed is slower than the rest. Makes more sense and less hassle when you have wheels and or tires worked on, IMHO.

Doc C