I just installed new tires on my 2004 ls430 and I keep getting a low tire lite even though all four tires have the same pressure. I have not checked the spare could that be the problem?

 

You need to re-initialize the system by pressing and holding the reset button near the drivers right knee.

 

What GRAND said, you have to re-initialize the system. The 430 does not use the direct read from the tire stem, it uses the ABS system to detect "air loss" by detecting variances in tire rotation.

You can conceivably lose all air in all tires at the same rate and the system would never trigger. That's what happened with mine. All four tires had somehow gone down to 22 psi and no light.