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Tire Pressure Sensor - WTF

19K views 39 replies 18 participants last post by  friendly_jacek 
#1 ·
Is driving me nuts. 2007 Limited. We never had a problem before. Two weeks ago the sensor goes on, I stop and check all 5 tires. All are at 32psi. I filled them to 34psi, no change. Drop the car off at the dealer and they say the sensors are fine. The dealer tells my wife " In the winter you need to add an extra 4-5 psi" I say Bull. My wife brings the car home with all 5 tires at 37psi. Everything was fine for about a week. Today once again the lights goes on. Buts is different, sometimes it stays lite, sometimes it flashes. Pressure is still at 37psi

34,000 tires are factory orgignal. Any ideas???
 
#5 ·
Your dealer is full of it. I have ten tires (two full sets) and run them all at 32 PSI with no problems. Even when it's zero degrees F. I never get a warning. 37 lbs is too high, especially in winter when you want as much rubber on the snow as possible. It sounds to me as though the computer sensor in the car is faulty; insist that they check it out thoroughly. Call Toyota Customer Service if they won't cooperate.
 
#6 ·
I called the dealer around 9am today and gave them hell for suggesting to my wife to raise the tire pressure. I dropped them down to 32ps last night. I then call customer service. I spent 55 minutes on hold before I hung up..........most be all the recall calls. The car is going back in on Monday. They are going to check the computer sensor. I'll leave a follow up once the problem is corrected.
 
#7 ·
I have had mine go off twice. Once for the spare tire which was in the low 20s and the other was right about the time cold weather hit my area. Now in my case the cold weather coupled with the tires I was down in the mid 20s on one or two tires. I put them back to 32 degrees and it's been fine since.

So the dealer isn't wrong about cold weather reading lower but if the tire is already at 32psi then it's not the issue.

Basic rules of checking tire pressure (I'm sure you know but for anyone reading this thread who doesn't).
Try to do it when the vehicle has sat at least few hours after driving, overnight if possible.
Check tire pressure during normal weather for whichever season your in.

When cold months are coming I try to go 1-2 psi over recommended values. Warm weather I err on the side of right at or 1 psi lower.

Good luck hopefully it's an easy fix and doesn't cost a ton if your out of warranty.
 
#10 ·
Carbon said:
zaitcev said:
Most likely a dead battery in one of the sensors.
I don't think that would fit the symptoms. If he goes to 37 PSI, the alert goes away.
That's exactly right. And also he said the TPMS light flashes sometimes. That indicates a malfunction in the ECU. A dead battery in a sensor wouldn't do that.
 
#11 ·
I have been checking this forum to see if anyone has ever mentioned any of the unique issues with the spare tire on 4.3 Rav4. This thread seemed like a good spot because it has a few other things that need some clarification.

The most interesting point I have learned is that Toyota (according to a well informed "factory man" who covers quite a few dealerships) has noted an unusually high failure rate of the sensor units in the spare tires! It is his opinion that the failure rate of the spare tire sensors (barring instances of tire-iron/TPS interaction) is twice that of the sensors in the other four (rolling) wheels. The reason he has surmised is "slamming the door".

I do not work for Toyota, nor Pacific International (the folks who make the sensors), but I have turned a wrench for over forty years…and I do know a few Toyota factory techs and lots of dealership-wrenches. For the most part, they share this opinion. After thinking about his premise, it does make sense; the sensors in the wheels are all the same…all made by Pacific, the same model, and in most cases mounted in the same model wheel. The only difference is that the shocks and jolts incurred by the rolling wheels are vertical, but the stresses incurred by the spare tire are horizontal (as in "SLAMMMM"!).

The other point that seems to need clarification is how the TPMS warning light works and what the different displays mean. When the light simply comes on and stays on, this denotes one of the five tires (yes…the TPMS ECU receiver, located in the right-side cargo compartment fender well, looks at all five tires) has transmitted a pressure below the preset alarm pressure (in this case around 26 psi) the light will turn on. It is the "BLINKING" light that is the troublesome issue. If, in fact, the TPMS warning light blinks for thirty-seconds and then stays lit, the problem is a TPMS system failure. The nature of the failure can be with any component of the TPMS system: an ECU problem, a receiver problem, or (the most likely) a transmitter problem.

In the case of the last Rav4 I worked on (2007) the owner was upset because the tire dealer repeatedly reset the TPMS light, only to have it come on again after approximately 25-minutes driving time. After noting the TPMS warning light come on at KOEO, but blink for thirty seconds and then staying on, I knew that it was a "system failure" of some sort. Yes…"system failure" sounds ominous, but it is the term Toyota (and Motor and Alldata) uses in the service manuals. At any rate, I first went from tire to tire with my Ateq VT30 monitor tool. When I got to the spare tire, there was no response…the sensor was dead. After replacing the sensor I found that the old one had a crack in the plastic where the metal valve stem meets sensor body. The rest of the repair required scanning all of the sensor ID's into the monitor and downloading them to my PC…and then registering the new spare tire's ID (and the location of each ID) into the Rav's ECU. The light issue was resolved.

Hope this explains the TPMS troubleshooting procedure and the spare tire issue.
 
#12 ·
No offense, Leo, but hogwash.

There is absolutely no way to design a TPMS sensor to be robust enough to hold up to road wheel acceleration rates in two axes, while being so delicate as to be damaged by the acceleration rates seen in a door slam in the third axis, without intentionally trying.
 
#14 ·
Best talk to some genuine techs before you shoot yourself in the foot…again.

If you have some facts, we would all like to hear them. If not, here's one: I've replaced some TPS units. Having the right tools made me the go-to guy in my area until the other shops invested in the latest all-in-one monitor/programmer units. In the five years before I retired I collected a box of dead TPS units. 23 of them are Pacific brand TPS units. Because the shop has to pay extra to dispose of the batteries in the TPS, I kept them. Most of them were damaged by folks using tire inflater, another bunch were broken during tire changes, and a few more were smashed by driving on a flat tire. But…I have three that were removed from the spare tires of Rav4's. That is 13%, which came out of tires that looked new…probably never made one turn on the road. That is way too high a percentage to right-off as coincidence. These TPS units saw no valve-stem damage (the tire-covers were all in fine shape). I can't imagine someone going to the trouble of wrestling the tire cover off, just to sabotage the TPS unit…not to mention refilling the tire with air and replacing the valve core after they "spiked" it. We had a rash of trouble when some kids learned how to "spike" TPS units by removing the valve core, drive a nail (or something long enough to break the transmitter right off of the valve stem) and replacing the valve core and cap. These three showed no sign of damage…aside from the fact that they don't transmit. No, these things died for some other reason, which didn't leave a trace (except for the one cracked TPS I mentioned). That is why I asked the tech rep about it.

And if you think it's dead batteries, try again. Most of the dead units (that were not smashed outright) still had batteries with 2.8 Volts or more. Check them yourself…you can drive the tip of a volt meter probe through the silicon filler easily enough to test the batteries. Maybe another reason why Toyota took the spare off of the door? You better gather more facts before you linch the messenger.
 
#15 ·
Best talk to some genuine techs before you shoot yourself in the foot…again.

If you have some facts, we would all like to hear them.
Hi Leo, and welcome to RAV4World!! I've been hanging around this forum for over 5 years and heard some strange stories, but I can't remember anyone with a bad TPMS sensor on the spare. I don't doubt that you found at least 3 that went bad for no reason, but this doesn't seem to be an epidemic. You'll find a lot more people on here who have had bursting VVT-i oil lines, broken sway bar links, and bad water pumps.

Those 3 Pacific sensors you mentioned probably have a bad battery. The 2450 lithium cell inside may be bad even if it's showing 2.8 volts. I've had these types of lithium cells that show the full 3.0 volts, but they drop to zero under any kind of load. And although they are advertised to have a lifespan of 10 years, many are going dead before then. I just can't believe that a TPMS sensor designed to be rugged enough to work inside a spinning tire in extreme temperature ranges, hitting potholes, etc. would fail due to a slamming door.

I went to the FCC site and entered the ID number of the sensors and got some nifty pictures. I would be curious if replacing the battery on one of those 3 sensors would bring it back to life?











If not, here's one: I've replaced some TPS units. Having the right tools made me the go-to guy in my area until the other shops invested in the latest all-in-one monitor/programmer units. In the five years before I retired I collected a box of dead TPS units. 23 of them are Pacific brand TPS units. Because the shop has to pay extra to dispose of the batteries in the TPS, I kept them. Most of them were damaged by folks using tire inflater, another bunch were broken during tire changes, and a few more were smashed by driving on a flat tire. But…I have three that were removed from the spare tires of Rav4's. That is 13%, which came out of tires that looked new…probably never made one turn on the road. That is way too high a percentage to right-off as coincidence. These TPS units saw no valve-stem damage (the tire-covers were all in fine shape). I can't imagine someone going to the trouble of wrestling the tire cover off, just to sabotage the TPS unit…not to mention refilling the tire with air and replacing the valve core after they "spiked" it. We had a rash of trouble when some kids learned how to "spike" TPS units by removing the valve core, drive a nail (or something long enough to break the transmitter right off of the valve stem) and replacing the valve core and cap. These three showed no sign of damage…aside from the fact that they don't transmit. No, these things died for some other reason, which didn't leave a trace (except for the one cracked TPS I mentioned). That is why I asked the tech rep about it.

And if you think it's dead batteries, try again. Most of the dead units (that were not smashed outright) still had batteries with 2.8 Volts or more. Check them yourself…you can drive the tip of a volt meter probe through the silicon filler easily enough to test the batteries. Maybe another reason why Toyota took the spare off of the door? You better gather more facts before you linch the messenger.[/QUOTE]
 
#16 ·
I didn't think that passing this tidbit along, from a source that I think is pretty knowledgable, would draw this much…attention. But, in deference to the points made, I thought I should check the voltage in the TPS unit I mentioned in my first post. It came out of an unused spare tire on a 2007 Rav4. Note that the three lug nuts holding this tire to the door looked like they had not been touched before I took them off and, judging by the amount of mud and crud in the bottom of the cover, I don't believe it was ever off of the car either.

Here it is:

Technology Electronic device Electronics Measuring instrument


Please note the Max reading of 3.39 volts. I had to use the Vantage because I could not hold the probes on the battery and take the picture at the same time. I am going to put a 1K resistor across the probes and check the battery again. If it is "near death", 7-milliamps should drop the voltage well enough. I realize that this one case does not prove the hypothesis one way or another, but it is something to consider. I'll report back what I find.
 
#17 ·
I didn't think that passing this tidbit along, from a source that I think is pretty knowledgable, would draw this much…attention.
Well, Leo, as an electronics tech I find this kind of thing interesting.....:thumbs_up:
 
#18 ·
James,

I have determined precisely why this TPS is dead…the bottom lead, from the negative side of the battery to the circuit board, is detached at the circuit board. The entire solder pad has pulled off and, judging by the amount of silicon under the solder pad, the pad had de-laminated from the board on day-1. The battery power was probably hanging on by a whisker…until "something" knocked it loose. BTW: The battery is still good, but it will not transmit even when I try to hold the pad onto the circuit board with an alligator clip.

When I get back to the shop, after Christmas, I'll check out some of the other units that don't have obvious damage. From what I see now, I'm more convinced the slamming door hypothesis is plausible. My point being that, because the battery and the circuit board lie in the same plane as the force from a jolt by the wheel being hit from the side, and because the two halves are held by the rather soft silicon, the heavier battery could easily be pulled away from the circuit board if the connection to the board is not solid…and the connection to the circuit board on this TPS was very poor. They didn't even thread the battery lead through the circuit board. It was simply soldered to the pad with a "puddle" of solder on the top. There is also a puddle of solder on the bottom, but it doesn't touch the battery lead.

This TPS probably did pass all the electrical tests (obviously…it did work for five years) but the mechanical connection of the negative battery lead was terrible. The lead should have passed through the board and been soldered on the top and bottom sides. This TPS failed because of a manufacturing screw-up.

LEO
 
#21 ·
My point being that, because the battery and the circuit board lie in the same plane as the force from a jolt by the wheel being hit from the side, and because the two halves are held by the rather soft silicon, the heavier battery could easily be pulled away from the circuit board if the connection to the board is not solid…and the connection to the circuit board on this TPS was very poor.
Consider the force input to the TPMS sensor if the road wheel sees a high vertical acceleration rate while the valve stem is at 3:00 or 9:00 - the battery solder connections would be stressed in the same way that you're envisioning in the door slamming scenario, just at a different angle.

Again - try to design a solder connection that will be robust in one direction, while being fragile in the transverse direction.
 
#19 ·
Nice post-mortem, Leo, thanks for that. As an electronics tech I have seen my share of broken solder joints and pads pulled off of boards. Another problem now is some governments are mandating lead-free solder which just doesn't work as well. I agree that for an electronic device designed for those punishing conditions, the soldering job was very poor.
 
#23 ·
I don't feel like getting into a discussion of the response of the leads to various force inputs, especially when neither of us can say with any certainty what support the silicone inside the sensor casing provides to the battery (especially in a spinning tire where the battery is continuously pinned against the bottom of the casing). This is the kind of design problem where engineers will simply specify a certain peel-off load to qualify the soldered connections and not bother with a detailed engineering analysis of the complete system - the non-linearity of having the battery constrained by silicone makes any finite element model of the complete sensor an exercise in guesswork. I agree with you that supporting the battery with two soldered connections is asking for failure - my only point is that in the average day in the life of a TPMS sensor, the ones in the road wheels are going to see a whole lot more acceleration events of greater magnitude than the spare will see in the occasional door slam.

I'd be very curious to know how many TPMS sensors get replaced at dealer shops because they've 'gone bad' before the vehicle ever gets into customer hands.
 
#24 ·
You have a good point, regarding the silicone filling. The support value would be hard to quantify for many reasons…including factoring in all the "voids" this particular TPS unit had. The back-side of the circuit board had very little silicone filling.

I can't speak to the premature failure of the Toyota TPS units, but, as I was commiserating with a fellow wrench about the ridiculously high "outrageous" prices of TPMS service tools (we were in the back of the MAC tool truck…speaking loud enough for the tool-guy to hear our complaints, which fell on deaf ears) he mentioned that our local Ford dealer had to replace "…more than a hundred of them under warranty". He knows this because he works at the local tire dealer were most of the work was done.

This brings up another point, which is my own opinion…take it as you wish; the price of the TPS units and service tools are far beyond reasonable. The TPS units are being manufactured by (literally) the millions. The fact that they still cost me around $50 each is price gouging. Then I must charge the poor customer to install it, rebalance the wheel, scan all of the wheels, and re-register the TPS units to the ECU…I have to charge the poor customer at least $100 so I can make a living. Then consider the $600+ I had to invest in the tools (and the new Snap On and Bar Tech units are much worse…over $2,500 each), it just galls me. The outcome will be more people deciding that the cost just isn't worth the benefits, and they will have a mechanic deactivate the system altogether. Seems like an example of greed deterring, what is otherwise, a good idea. Just my $.02.
 
#27 ·
my TPMS light just came on again. the first time it happened it occurred while i was driving home the day i bought the rav4! i had to drive back 30 minutes to the dealer who wanted to charge me for the TPMS but saw that i just purchased the vehicle and reluctantly replaced it without charge. it has been very cold and snowy outside here in the DMV but i will check the tire pressure on all tires but i have a bad feeling it is a TPMS sensor malfunctioning. is there any way to disable the TPMS completely? EDIT: nvm i found the sticky in the interior section, wow this site is awesome!!!!!
 
#28 ·
I know I am repeating myself, but this is worth remembering…understanding(?)

If, on startup, the TPWS light comes on "solid" and then goes off, your system is normal. If it comes on solid for a few seconds, goes out for just a moment and comes on solid…you have a tire with low pressure (below 26 psi). It the light comes on solid for a moment, then blinks for thirty seconds, and then stays on solid…you have a TPM system failure. That failure could be with any component: any of the five sensors, the antenna (behind the right-side cargo area panel), the ECU (passengers-side kick panel), or the wiring harness. Point is, it could be anything from a dead battery in one of the TPS units to a failure of the ECU…or anything in between. The only way to determine precisely what the problem is, is to have someone with TechStream scan the error code (or look at the live data) to see exactly what the light is telling you. And don't go to a tire dealer to have this done. They don't have the tools (and sometimes not the knowhow). They will simply reset the light and charge you $25. If the problem is a system failure, you will get about 30-minutes away from their shop and the light will come back on. Fixing this is a job for a shop with the proper tools (or one of our forum members who invested $25 on the Techstream software and connector).

LEO
 
#31 ·
Truer words were never written. And, can you imagine the howl from the owners when they get rip'd off at the current $145 dealer price to replace ONE sensor. It's gonna get ugly.
Don't you think that with the millions of the sensors being made that someone will come up with rebuilts at reasonable prices?
 
#32 ·
They may come out with rebuild's, but when you look at these things closely…hell, they are selling new cell phones for less than $20. If they can do that, TPS manufacturers sure can make a new TPS unit for under $20 each…and make 100% profit while they're at it. I have no doubt that they're current profit margins are in the triple digits. It's just a matter of time, when half the cars on the road have illuminated TPWS lights (or have them jumper'd out at the ECU), someone will come out with a "commodity" TPS unit.

All The Best,
LEO
 
#34 ·
Leaking value stems with TPMS

All,
I have a slow leak between the valve stem and wheel on an '06 with Al wheels; I've been told that apart from taking the tire of the wheel, cleaning up the value hole and re-assembling, if that doesn't do the job the only other cure for a leak around the stem is to replace the entire TPMS unit ($120 all in).

Such a deal! Now I just carry a tire pump with me for weekly re-inflation, but that's not a great solution. Does anyone know if there is a kit to repair the seal between the stem and the wheel without replacing the entire unit?

Thanks!
 
#35 ·
Does anyone know if there is a kit to repair the seal between the stem and the wheel without replacing the entire unit?

Thanks!
Yeah, any decent tire shop will be able to rebuild the seals on the sensor, and they'd better not charge you more than their standard mounting fee with TPMS service. Discount Tire Direct charges $3 for the seal kit, and I'd expect the price to be comparable at any local shop.
 
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