Installed a sub to my 250 this weekend. Once I had everything back together I get a "Check System" warning with a flashing TPMS light. Would having the power disconnected for so long cause the issue?

Anything I should check before taking it in to have the sensors checked?

 

Just a Coincidence....
I've had my battery disconnected for a week before and no TPMS light.

Is there anything you should check? Um ya ,tire pressures .Cold fronts decreases pressure in tires.

If that doesn't work ,try resetting it
from the manual
1. Park the vehicle in safe place and turn the "ENGINE START STOP" switch OFF.
2. Adjust the tire pressure to the specified pressure.
3. Start the engine. Make sure to adjust the tire pressure to the specified level. The tire inflation pressure warning system will operate based on this pressure level.

1) The tire pressure initialization setting display
Continue to press the "<" or ">" switch until the initialization setting display appears. It may take several minutes to complete the setting. Wait for several minutes before turning the engine switch OFF if necessary.
2) Recording tire pressure settings
Press the ON/OFF button for more than 3 seconds. At this time, the tire inflation pressure warning indicator flashes 3 times and the message ("PRESSURE INITIAL") showing that the initial setting is complete is displayed on the multi-information display.

 

I know what the TPMS monitors.. lol..

I meant was there anything other than the sensors themselves that could have gone out/been reset electronically. Tire pressures are fine, checked em today and they are brand new tires. Will run by the shop and have them looked at.

That initialization sounds like a sure bet, will try it.

 

I think there is a blue box in the spare trunk or around that, and that box is the tpms monitor ECU, there must be some plugs not reconnect after you have the sub replace. Did you replace the sub your self or someone did it for you?

 

^^According to the parts diagram,the TPMS ECU is up under the dash behind the Nav area. See #2 in the parts diagram. Every Toyota I've ever worked on has the TPMS ECU somewhere up under the dash.
But you may be on to something as there is an antenna(#3) for it in the rear/left drivers side somewhere that might have gotten unplugged and it's not picking up the radio signal.

 

How old is the car? Maybe the battery of the sensor?