Rep Power: 0

I have a 2008 Honda Civic LX sedan with Automatic transmission. Two months ago I had my oil changed, but I don't think they rotated the tires. A few weeks later, I was driving in a bad rain storm and my TPMS light came on. NOTE: NOT the LOW TIRE PRESSURE (!) light. The TPMS light was on continuously and then I realized my rear passenger tire was leaking. The tire had a leaky valve core (I sprayed in the valve with windex and it bubbled like crazy.) So I went to WalMart and bought Slime brand 4 way valve tool with 4 valve cores. The package says "(!) Tire Sensor Safe" but who knows if they actually are. I unscrewed the old valve core and replaced it with a new one. After a few days of driving with correct tire pressure (I put 33 in all tires), the TPMS light went off. Now it seems to go off and on about twice a day while I drive around. Sometimes it's on, sometimes it's off.

Around the same time as replacing the valve core, I also had to replace my 3rd clutch gear automatic pressure switch because I was experiencing bad shifting, check engine light had come on (and would turn off at times) and had codes P0847 and P0756. Since then shifting has seemed better and the check engine light has not come back on.

Is my only option to head somewhere where they have a TPMS tool to have them do a reading to figure out what the problem is? My tire pressure has been fine, no drops.

 
Rep Power: 221

sensor could be going bad, car is 10 years old, could still have the original sensors

 
Rep Power: 517

Pretty much, unless you want to buy the equipment necessary to deal with it.

Typical cause is a failing sensor, could be any of the 4
Electronics devices in the car can cause weird issues too, like laptop, cellphone, charger, inverter, etc. can cause RF interference that affects TPMS

 
Rep Power: 0

I tried unplugging my phone charger but nothing changed. I don't have any other electronic devices that I know of, and I have been using the same phone charger since well before the TPMS light came on. I thought fixing the leaky valve core would do the trick. Should I try putting in a new valve core to see if has less "reaction" on the TPMS? The fact that the TPMS light went off after changing the valve core makes me think that it's an issue with that tire's sensor, and not one of the others. But maybe it's just a coincidence? Of course now the TPMS light keeps coming on and off throughout the day.

 
Rep Power: 517

Nah, the issue is electronic related, not pressure and leakage.



You already knew low tire pressure turns on the (!) icon.
The letters TPMS is the system warning light that tells you something more than pressure is wrong. There's a fault code stored in the TPMS system to help a troubleshooter.
Most of the time it's one (or more) failed (or failing) sensor in a wheel. . If one stops transmitting for whatever reason, the system sees that as a fault.

Yes a failing sensor can be intermittently working, then not. Seemingly at random.(weak battery inside a sensor can do this)

Of course a sensor is not the only possible cause, that's why I mentioned the other stuff. There are many different codes for many different possible faults.