Need Help w/ Tire Pressure Light After Driving

[James MacArthur]

I just purchased my first Lexus. It is a 2008 Lexus IS250 with 74,000 miles. After driver about 30 miles or so the tire pressure light comes on and will not go off. The first time this did it, I checked the pressure in the tires and it was high (the car had been sitting all night) at  around 42 in each tire (the door says 35 for the fronts & 38 for the rears). I drove to the tire shop and they did not see anything wrong with the tires but we lowered the pressure to 38 in the fronts and 40 in the rears. Driving to and from the tire dealer, the light was off. Later that day though, while driving on the freeway, the light came back on. Later in the day I discovered that the pressure was back up to around 42 in each tire (this was just after driving for awhile). I lowered the tire pressure to 35 in the fronts and 38 in the rears but the light did not go off in my 8 mile drive home. Any help for this problem would be appreciated. 

[GDixon]

Two things to try (if they apply to how your IS is equipped).

1. Check the spare tire pressure if it is a full spare. It is monitored.

2. Reset the TPM system by using the button under the driver side dash.

 

At least these are the procedures for an RX.

It takes a little bit of driving, maybe 10 to 20 minutes, for the TPM system to catch up to any changes.

Try this thread for more info:

http://us.lexusownersclub.com/forums/topic/84181-tire-pressure-indicator/#comment-495423

[James MacArthur]

Thanks for the info Gary. The spare is not full size so I don't think its monitored. Although there is no pressure in the donut right now. The pressure is normal on the car right now and of course the light is still on (but that may be just because I have not yet driven it this morning. The big issue seems to be when I am driving. The light will come on after driving it awhile. I think will take it out for a spin tomorrow and see what happens. Thanks Again.

[James MacArthur]

Well it turns out that I actually had a faulty tire pressure sensor. Go figure.

[GDixon]

I read somewhere that the average life of those sensors was around 8 years. They don't come cheap as you likely discovered. And then there is some sort of matching that needs to be done by computer. UGH.

My RX is 8 years old and the TPM light just went on again yesterday. It happened once before and the spare was low. All four tires are properly inflated so dropping and checking the spare is next.

I may end up being in the same boat as you. Ahh...as they say, "a misery shared is .... blah, blah, blah."

[GDixon]

Just an update to my post re: TPM warning light..

The tire pressure in the spare was down to 25 psi. Second time it has happened over the life of the RX.

I don't think the problem is justification to junk the car.