Friday, August 03, 2018


     My RX350 has tire pressure sensors.  Probably.  So far, I have good tire pressure and a warning icon showing on the dash.  I'm either doing the setting procedure wrong or some part of the system isn't working.

     So there's a project for the weekend.


JPD said...

Roberta, 40# of pressure is for the tires on your Harley motorcycle. Not the RX350. Biker chicks.....gotta luv'em.

John said...

It is possible that, depending on the age of the sensors, the batteries in the TPMS have expired. Possibly 1 or more still have enough juice to transmit a signal, but if your tires are properly inflated to manufacturer's specification, likely 1 or more sensor needs replacement. They were not meant to last forever.

Divemedic said...

The transmitter is part of your tire stem (the part inside the rim). It contains a battery that goes bad after a time. When this happens, the entire sensor must be replaced. They cost about $40, and the car must be programmed to recognize the new sensors. This requires a special reader which for many manufacturers is expensive, which means only the dealer and some of the larger tire shops have them.

John said...

Our eight year old Forester began to give tire pressure alerts at the beginning of last winter.
After pulling over a number of times and checking all tire pressures including the spare, the alert was put into the "little boy crying wolf" folder.
As soon as spring came the alerts stopped.
I check all our tires at regular intervals with a digital tire pressure gauge, and I field calibrated the gauge against another digital gauge, and several mechanical gauges.
As John above said, the monitors run on a battery and one or more need replacing.
Any warning device that gives multiple false alerts is going to get ignored and the cost of replacing all the monitors is around four to five hundred dollars.
We are planning on having the job done just before it gets cold.
The job requires that each tire be removed, then the bead has to be broken in the area of the TPMS and the monitor changed.
That is a straightforward mechanical job, but then the car's electronics have to be told the serial number of the new TPMS and the old serials have to be deleted.
And depending on the scope of the job, the tires may need to be balanced.
If I had known the problems and cost of the failing TPMS sensors, I would have had them replaced the last time we got new tires.
Once you have determined the tire pressures are fine, a small square of electrician's "silences" the false alert.
Our state doesn't require that the TPMS be operating to pass the annual safety inspection, but I would prefer to have the safety warning system working.

fillyjonk said...

In my experience, tire-pressure sensors are not great. They give many false positives.
(Granted, my sample size here is 2, but one is a Ford and one is a Toyota....)

I also had my Ford sensors give me what I thought was a false positive, checked the tires, they all seemed fine; several hours later one went flat out on the highway (I had rolled over a nail that I was apparently parked on top of when I inspected the tires)

I still think monthly (or biweekly, which would be better) pressure checks with an old-fashioned gauge make more sense.

Mike V said...

As everyone else has mentioned, it’s probably a faulty tire sensor.

mostly cajun said...

My Honda Fit is seven years old. I just had to replace the batteries in the tire pressure sensors. Mine are mounted on a valve stem assembly INSIDE the wheel.

I let the dealer do it.

Will said...

These sensors are critical only on low profile (high performance/sporty) tires. Those can go nearly flat while driving on the highway, and you won't really notice a degradation in handling. That is, until the tire starts thumping, which is your signal to calculate the cost of replacing the destroyed tire.

It MIGHT be cheaper to add the external tire stem cap sensors that talk to your phone, and wait 'til your next tire purchase to consider the cost of fixing the factory system.

pigpen51 said...

I was surprised to see you mention this, since I had the same thing happen Monday. A sensor on my Pontiac Torrent gave me the low tire pressure in left side, rear tire.
I could not see it, but I checked the pressure, and I was at about 23-25 lbs. of pressure in that one tire. I pumped it up, and I will check it over the next few weeks, to see if there was a hole in the tire, or why it happened.
I do have to say, though, that I was impressed by the function of the sensor. It was a very good thing to have, since I avoided having a tire go completely flat, with the corresponding pain in the rear of having to change a tire. And now that I am on notice, I am going to be able to hopefully stay ahead of it, and get it either fixed or replaced if it causes me anymore trouble. And I should still have the sensors as another way to warn me, if I am not quick enough to check it.

Anonymous said...

Also check the pressure in the spare. Had that drive me nuts on the late (not so) great Ford Windstar once.

Roberta X said...

First things first -- if what I'm reading for the setting procedure is correct, I've been doing it wrong.

D.W. Drang said...

I tend to distrust these things. The one on my Journey has been coming on and going out for a few years, maybe dead batteries as others have said.

(Army 5 tons had a tire pressure monitoring system, that would let you adjust the pressure from inside the cab, to match local conditions. They were notoriously unreliable, and usually disconnected.)

OTOH, one year Mrs. Drang and I flew back east to visit family. We spent a few days with my parents in TN, then drove up to MI. Somewhere in Ohio Dad turned the wheel over to me. I didn't even know there was a monitoring system, and when the light came on I didn't notice it, because it was not exactly prominent on the dash. So when one tire gave out, it came as a surprise.

(I will say that I was most impressed by how well that Ford handled with one tire gone. I didn't realize the racket was the tire shredding until I saw the debris in the rear-view, it sounded like a Huey overhead. We were near Wright-Patterson, so it was plausible...)

Anonymous said...

The dealer/Firestone/whoever SHOULD replace the batteries if you buy a new tire. (Since you have to take the tire off the wheel.) I just bought 4 and before they could give me the price on "what is the total cost" they had to ask if I had the sensors.

The tree hugging community loves the fact that if your tires are inflated, you get better gas mileage. But I think the real reason that the law was passed is because the wireless signal makes it stupidly easy to follow a car from a distance, once you figure out what the 4 wireless tags are...

(Somebody - Hak5 maybe - had a short video on that.)

danno said...

$.02 The Truck's TPS alarm had been on for several months. I checked PSI's several times but still the TPS alert droned. My friendly local gearhead asked "Have you checked the spare". For inconvenient reasons that did not happen.

However today, after replacing all four main wheels, It reset within 0.5 mile. So it would seem the TPS alert is not just a Tire Pressure alert, but for what ever reasons "we think your tires need attention now".

Again $.02.. HTH