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I have a 2008 cabrio. The TPMS light comes on and flashes 40 -50 times before staying on. It turns off at random times as I'm driving. The tire pressure checks out OK.

Any ideas folks??
 

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The most likely thing is one or more of the tire pressure sensors is dying. The batteries do not last forever. A proper scan tool or tire pressure sensor tool can probably read the data from the sensors to give a direction. If a tire pressure sensor goes off-line that will set a fault and cause the light to illuminate or flash. One would need to scan the system for a starting place.
 

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There is another possibility. My Mazda B2300 did the same thing. I did not relish replacing 4 batteries because that "might" be the cause. I hunted around on YouTube and found a video from a Ford tech I trust. The TPMS sensors communicate to the vehicles computer using radio transmission. It seems that on occasion they get customers who come in with this complaint yet they can find nothing wrong. They hit on the cause being radio interference caused by the customers USB adapters used to charge phones, etc. They tell the customer to remove all the USB adapters and drive for a week and see if it goes away. It seems the cheap adapters you buy for a couple of dollars are the culprits, not name brand charge cords you get with your phone.

Well I disconnected all my devices and drove 300 miles and had no problems. So I replaced all the cheap adapters and for the last 12,000 miles I've had no problems. Cheaper than replacing sensor batteries and still having the problem.
 

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Your TPMS ECU may be blown

Every time I started my 2008 the TPMS warning light flashed for ~20sec and then stayed on. I had the TPMS units in the wheels checked and they were ok so the dealer deleted the fault code. That fixed the problem for about 2miles and then the same thing happened again - TPMS warning light flashed and then stayed on.

I did a bit of research and noted where the TPMS ECU is located (about 12in above your brake pedal), bought a used one on eBay and fitted it. It took about 10mins to remove the old one and fit the replacement because I needed to find a towel so my shoulder would not get dirty on the rubber floor mat; otherwise it would have taken 5mins. lol

Problem solved!

You'll need to buy one of these....
 

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True, but as Rustedwrench said,the batteries don't last forever. I'm needing to replace the tires on one of my 09s and I'm considering replacing the TPMS sensors (batteries are not replaceable) simply because the batteries are coming up on 8 years old. I've read that the life expectancy is about seven years or so.
I know a piece of electrical tape will cover the TPMS warning light, but I prefer to have the system operational; it's an invaluable early-warning system.
 

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Update

I did replace my tires and TPMS sensors. I used Tire Rack in South Bend, IN. They tested my new eBay sensors and installed them. They advised that the pressures were set and the TPMS was reset. After a short drive, the TPMS light came on. I tried several resets to no avail and assumed maybe a sensor bit the dust. After shutting the car off for a while, I was able to reset the system but the light came back on shortly after I began driving.

When I got back, I did a search on SCOA regarding TPMS. I found this thread, but more importantly, I saw post (3) above.

I rarely use my phone charger, but sure enough it was plugged in. I got rid of the charger and did another reset and it's all good now.

Thanks HMilton!
 

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So glad I didn't opt for this option on my new 453. My old 451 sensors were always giving me errors and were so expensive to replace.
 
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