So first off, my tire pressure is not low. My problem is whenever i turn my truck on, the tire pressure light flashes for about a minute or so then just stays on. What does this mean and whats the best way to fix it? Ive had after market tires for about a year or so but had to get a patch when i had a leak and this is when the problem first occurred. I always keep my pressure at 43 psi too

One more question, not sure it should be on this section but whenever im at low rpms (mostly after i turn my truck on and make my first turn and gas the sob) there is a rattle like sound in my under carriage but after awhile it just goes away. What would be causing this?

fyi -
2007 ford f150 4x4

 

Mind cleaning up your questions a little, I dont what your talking about.

 

What tire pressure are you using? OE tires and the recommended pressure, or aftermarket and something else. If OE tires with recommended pressure, it is more than likely a bad sensor or monitor. Could be just a bad battery in one of the sensors.
If using aftermarket tires and a pressure of over 50 psi, you could have destroyed the sensors as they have a max stamped on them of 50 psi. At least the ones I had on my 07 stated that.

 

If you got new tires and had a shop install them, they may have not put the sensors in your new tires. I know mine couldn't fit inside my 38x15.5 mud graps so I just deal with the light on for now until I get around to programming it to shut it off. As for the rattle noise...I've got no idea on that....

 

wait if i get the OP's post correct, the TPMS light comes on only when you use your turn signals? that's very strange and sounds like there's an electrical issue somewhere in the truck, possibly in the gauge cluster or behind the dash. i'd get this checked out by the dealer as it definitely doesn't sound like an easy DIY fix.

edit: just reread it...sounds like you meant to say when you turn your truck on the TPMS light comes on. sounds like a bad sensor. when i went to training on TPMS, we were told the batteries were designed to last between 5-10 years, but i've seen quite a few that have lasted only half that.

 

Flashing for 70 seconds and then remains constant indicates a problem other then low pressure. See this link

http://www.aa1car.com/library/tpms_ford_f150.htm