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TPMS/actual psi differ?

Goin2drt

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Depends on model year of the JL, what one sees behavior wise in regard to this TPMS stuff.
This is accurate right here.

TPMS - the actual TPMS will "wake up" and send a signal when either rotating OR adding/releasing PSI.

The Jeep/Car/Truck - the update to the vehicle is all dependent on the vehicle if it is ready to receive the update.

ALL JL Jeeps should operate this way - As long as the Jeep is on in the run mode (2 pushes of the button without starting) or engine running then it will be ready to accept the signal and the PSI on your EVIC should change. Usually there will be a little lag by about a couple PSI.
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Chupacabra

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TPMS shows 40, actual shows 32-33….what gives? Any suggestions/input how to fix?
If it's that far off I suspect your gauge is bad. Do you have another gauge you can try to see what it says? Mine is dead nuts on with a fairly decent mechanical pressure gauge.
 

JABCAT

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If your TPMS disagrees with your gauge, the gauge is most likely wrong. My experience with TPMS is they are accurate (liability issues). Remember the Firestone Roll overs on the ford SUVs a while back. That is why the low pressure alarm is set with any tire <30psi and it takes aftermarket programmers to change. The dealer will not do it.
The Ford/Firestone issue was the recommended pressures were too low, not that the TPMS wasn't accurate. I can tell you the TPMS on my wife's '20 GC is off by 2-4 on every tire from the gauge ( I have multiple gauges). Those same gauges are spot on with my other two vehicles' TPMS.
 

Goin2drt

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The Ford/Firestone issue was the recommended pressures were too low, not that the TPMS wasn't accurate. I can tell you the TPMS on my wife's '20 GC is off by 2-4 on every tire from the gauge ( I have multiple gauges). Those same gauges are spot on with my other two vehicles' TPMS.
0-3 off is going to be normal for a TPMS system. Some are better than others. You can have 4 different gauges plus the TPMS giving you different readings. If they are off by a couple that is going to be normal. If your TPMS matches EXACTLY to your particular gauge you are great. If TPMS is off by a few that does mean your TPMS is not working or bad.

TPMS is a safety feature for when you have a blow out or puncture. It is not to regulate the perfect and exact PSI so that you can have perfect tire wear. That is what a high quality (usually digital) gauge is for.
 

JayJay

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Depends on model year of the JL, what one sees behavior wise in regard to this TPMS stuff.
Kinda like whether or not the full length owner's manual is supplied from the factory. ;)
 

JJMalone

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Most overlook that fact that TPMS sensors measure absolute tire pressure. Any gauge measuring on the outside of the tire is measuring differential pressure; that is how much greater is the inside pressure from the outside pressure. This pressure will vary with altitude and barometric pressure whereas the TPMS sensor only measures inside-the-tire pressure. This is one reason to trust your TPMS sensors more than a mechanical gauge or digital which might not be any better than mechanical.
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