One of the tire relays in my car is low on battery. Would it be more economical to replace all of them at once or just the one that is low battery?
Legit one of the most useless money grabbing things invented for cars. These overwhelming over-engineered underperforming components are much expense for a whole lot of nothing. All for the sake of having one more part for the shop to replace I guess? Just pull the fuse that powers that specific light to your dash LOL.
If you legit want to go replace it, just do the one at a time. It's really not worth much unless you live in an area that runs over construction material 24/7
Once you find out the cost of replacement of all those sensors, … you probably will want to just go get a cheap tire pressure gauge, set a reminder on your phone to check tires pressures regularly with your new gage, … and ignore the tire pressure monitoring system all together! And that pesky light in a dash glowing? There is a solution to that: small square of a masking tape, … cover it with it!
F.S.
If you absolutely must have TPMS system on your car, and you don’t want to use a manual tire gauge to check the tire pressures or an aftermarket device like Scotty shows below (see video), and it’s in the time frame when the batteries can go out on those (generally 5-10 years), and you have the budget for it already, I would change all of them and be done with it for another 5-10 years. But that will easily be (about) $250+ for parts alone. How much is it worth it to you? Me personally, I would pay it since I enjoy having that information (PSI/temp) displayed to me at all times. However, for one of my vehicles - the TPMS is very basic and it does not list the tire pressure or temperature in my instrument cluster or screen (it just says ‘Low Tire’), so in that case it was not worth it to me to replace them. I just went with an aftermarket unit Scotty recommended, but those BTW can be hit or miss in terms of quality and how long they last (Chinese quality).
https://m.youtube.com/watch?v=0qMbPmUseoc