OBP

I installed a set of rims and winter tires ( non RFT ) that I bought used from another SC430 owner. The TPMS sensors are supposed to be already installed in these winter tires. I have the colors and codes for all 4 of these sensors (took them from the previous owner's receipt) but I have not programmed them into the TPMS in my car. As far as I know, the TPMS in my car is programmed at the MAIN setting for the OEM rims, not the winter tires and rims. Don't have the codes for these OEM rims with sensors cos they were already programmed when I bought the car from a Lexus dealer. And I know the TPMS was working well a few mths ago because I took a blowout and the thing was beeping and it lit up.

So here is the qn: I was expecting my TPMS warning light to come on once I put the winter tires and rims on. But it did not. Absolutely nothing - just like driving with my old set of tires on OEM rims except they ride better because they are not runflats. No TPMS warning light, no beeps, nothing.

So does this mean my original MAIN TPMS settings in my car by coincidence had the same codes as the TPMS in my newly bought winter tires ?

How can I be sure my TPMS hasn't totally shut down for some reason ? I need it now more than before because these winter tires are not runflats.

Would appreciate any views and advice.

Thanks

OBP

Oh BTW I have an 05 SC430

Harold57

You can always let the air out of a tire down to the 20 psi range and see if it registers a fault. (Then air the tire back up!)

Yes

you actually need it less with regular tires than with runflats. with regular tires, you can see if your tire is low or if you have a flat. with runflats, your tire appears inflated even when it's not. and you'll keep driving until you damage it beyond repair. that's the main reason they put TPS in the car.

that said, i'd try what harold said and let the pressure out to see if the sensor goes off.

OBP

I reduced pressure in the front right and rear left tires to 22 psi. The TPMS light did not come on. This was with the switch in the main setting. Then, when I switched over to the secondary setting, even with fully inflated tires, the TPMS light came on.

Looks like the TPMS in the main setting will only work with my OEM rims and tires and for some reason, I need to re-register the winter tires in the secondary setting. Was hoping to use the main setting for both sets of tires if by some coincidence, the codes turned out to be the same.

Anyone with any other perspective ? Still curious about why there was no TPMS warning light when I reduced the tire pressure with the unregistered winter tires.

edinlexv8

iTrader: (2)

I have no answer for your problem but I am very interested to know what is the profile of the winter tyres you are using.

OBP

It is a Tire Rack recommended minus size: 225/55/16 Bridgestone Blizzaks with an H speed rating. They're about 3/4 of an inch narrower than the OEM size. They work very well up to 90 MPH - might do well beyond that but I have not tested higher speeds, yet. Like the look of the OEM 18s better though.

talwang

iTrader: (4)

It could be the sensors in your old wheels are still near by sending all the signal to the TPMS receiver.

Why don't you deflate all of your original rft tires to see if the TPMS light will stay on for good?

OBP

Thanks - I thought of that, which is why I drove around for quite a while in the new winter tires with unregistered TPMS. Still no TPMS light. I figure once I left the garage, even if the winter tires were fully inflated, the TPMS light should have lit after a while. I started the engine at least three times while running various errands 2 or 3 miles from home. Still no TPMS light. We'll see what the dealer has to say.

OBP

So here is the answer after talking to the Lexus tech (not the service adviser)directly: When I took off the OEM rims and tires, the car's computer automatically set the default trigger for low tire pressure warning to negative 15 psi. So that is why there was no light lit even when I reduced tire pressure to 22 psi.

Now my winters are set for secondary and my MAIN is set for my OEM, both with a 27 psi trigger. And I am supposed to be able to swap rims and tires in spring next year and switch to MAIN with no problem.

Cost of knowledge: $118 total.

Oh well...

talwang

iTrader: (4)

Hmm... it doesn't sound right. At least, the info does not sound complete to me.

so that means I don't need to disable the TPMS when I have aftermarket wheels with no tire sensors?
I know it is NOT true.

Since you have taken off your original wheels and automatically reset the computer to -15psi, it also means your TPMS warning light won't lit if you deflate your original tires now.
You can verify his story by setting it to MAIN and deflating your original RFT tires.
He may be right or it may just take longer to trigger the tpms light when all sensors are away at a distance at the same time.

Deflating your second set of snow tires has nothing to do with this all along when it is set to MAIN.

Yes

that explanation sounds a little fishy to me too. when i changed my wheels, i drove my car for a week with no sensors and it never reset to -15psi. as long as they fixed it, that's all that matters. but i don't think your service advisor knew what he was talking about. which isn't too surprising. i just had to tell mine that the daytime running lights could be turned off in the c best settings. then had to actually pull it up on CL and show him which setting it was when he told me it couldn't be done. the actual lexus techs probably know their stuff. but the advisors are mostly clueless.