Low Tire Pressure Lights On All The Time

[flowerbuyer]

Our 2004 Lexus LS 430's tire pressure light is on all the time, and the tire pressure is where it should be.

Does anyone else have this problem?

If so, what can be done about it without it costing a fortune?

Thank you

[curiousB]

If tires are confirmed as properly inflated then there is a reset button just above driver's right knee hidden under the dash. Follow the manuals instructions on how to reset.

The car doesn't in fact measure tire pressure. Instead it compares the revolutions of the wheel against each other and to the odometer. If a tire is low it is smaller and over the course of time will turn more that the rest. When this happens over a certain threshold the low tire indicator is turned on.

It needs to be reset whenever you rotate or install new tires. A local tire dealer would probably be unaware of this feature.

[GDixon]

Our 2004 Lexus LS 430's tire pressure light is on all the time, and the tire pressure is where it should be.

Does anyone else have this problem?

If so, what can be done about it without it costing a fortune?

Thank you

Check the spare tire. In most Lexus models it is monitored also.

[curiousB]

Check the spare tire. In most Lexus models it is monitored also.

Not this model. As mentioned it doesn't have pressure sensors in the wheel. Rather it counts revoutions of the wheel. I think '05 and later went to in wheel pressure sensors.

[VBdenny]

I can't speak for Lexus but a friend had a Buick that they low tire pressure indicator light came on. I fixed the leak in the tire and set all the pressures but the light stayed on. I looked in the owner's manual and it described the procedure for turning it off. Worth a look

[gunterlich]

I also have the problem on my LS 430 since I put new tires on. I have reset the tire pressure button a few times to no avail. Does the system check for low tire pressure only or does it send an alarm if all tires are overinflated ? - they put in 36 psi instead of 32 when they put on the tires

[curiousB]

I also have the problem on my LS 430 since I put new tires on. I have reset the tire pressure button a few times to no avail. Does the system check for low tire pressure only or does it send an alarm if all tires are overinflated ? - they put in 36 psi instead of 32 when they put on the tires

As mentioned there is no pressure measurement device in the wheels. Instead the car's ECU counts wheel revolutions and compares to each other and the odometer. Under inflated tires will turn more than properly inflated tires to cover the same distance.

Double check on how to reset the indicator. There is a procedure that reinitializes it rather than resets it. You want to reinitialze. Its in the user manual. Here is the procedure from service manual:

[gunterlich]

Thanks CuriousB! I appreciate the help!

Since you are knowledgable on the subject, I have some more questions. The first time I pushed the reset button (5 sec +) I had my head near the pedals to make sure I hit the right button so I could not see any messages on the display. There was no message when I got my head back up. When I pushed it again while watching the display, there was no message either. Question is, how long does the tire pressure reinitializion message stay on and should it come up each time I press the button or just the first time?

Thanks again

[curiousB]

I haven't done it for many months so honestly don't recall. I do remember it was important to follow the procedure to the letter to get it to initialize. My car has the smart keys feature so there are actually two buttons beside each other so its’ easy to get them mixed up. That compounded with its strange location make this more diffiicult than it should be.

[gunterlich]

Thanks CuriousB:

Right on - that is why I did not watch the display while pushing the button the first time. I 'll have to do some more research on the subject.

Thanks again

[gunterlich]

Hi CuriousB:

Made some progress: Played with my system and (1) the pressure initialization message comes on after pressing the button for about 7 seconds - but it only stays up for about 5 seconds (or less) before it disappears again; and (2) the message comes on every time the button is pressed. So if you have your head by the pedals to find the button, the message will be gone by the time you look at the display.

Now I'll drive car and I'll see if the 'low tire pressure' message reappears after a while.

Phoned a local Lexus dealer service department. They told me that "the pressure initialization may be out of sync with the ECU. To avoid this problem we keep the engine running while changing the tires". Hmmmmm. Interesting! But sounds like an urban legend to me.

Phoned another service deptartment and they did not subscribe to the above method - but they told me that "these cars were so complex and I should just bring it in". Hmmm.

Neither could tell me when the message appears and how long it stays up. I am happy to report, however that nobody suggested exorcism or sacrificing a goat to dispell the haunting 'low tire pressure' message syndrome.

[curiousB]

funny, a bit sad that a dealer, the guys with the special education and training for these cars, don't truly understand them. Worse yet they charge premium labor rates.....

Anyway I believe in more recent Lexus's they went to the pressure sensors in each tire. Maybe this counting revolutions scheme has more problems than it was worth and they reverted to more tradition method.

They guy and the ECU theory sounds like he's just guessing and just spreading FUD to scare you....

[gunterlich]

Hi CuriousB:

I think one of the problems is that you only get to talk to the 'sevice advisors' who have good manners but they really don't have a good grasp of the technology. Yes, as the man said, these cars are getting more complex. So what you need is people that are properly trained and experienced in the appropiate science and technology, not just 'monkey see monkey do' from an 8 week training session. What you need in these shops are perhaps people like competent automotive, mechanical or electrical engineers for appropriate consultation. There should be quite a few available at this time.

[amarslex430]

Hi CuriousB:

I think one of the problems is that you only get to talk to the 'sevice advisors' who have good manners but they really don't have a good grasp of the technology. Yes, as the man said, these cars are getting more complex. So what you need is people that are properly trained and experienced in the appropiate science and technology, not just 'monkey see monkey do' from an 8 week training session. What you need in these shops are perhaps people like competent automotive, mechanical or electrical engineers for appropriate consultation. There should be quite a few available at this time.

you may have a bad sensor on one of your tires.

[FRED DERF]

My 05 LS430 has been re-set a dozen times and I still have the Low tire idiot light on. I have been told that the control module has a battery on it and that it will not store the reset numbers. Does anyone else have this problem?

[VBdenny]

Not many people care much for the TPS idiot light. Luckily, I can call up the exact pressures of the tires on screen. That is something that probably should be on every car. The light tells you very little.