Hey everyone, My TPMS light came on today. Perhaps because of sudden cold weather up North here. All tires were pretty close to 30psi. (winter tires were installed recently and I didn’t check pressure afterwards). I reset them all to 35 and the light has gone off. My question is, what triggers the warning? Is it deviation of any tire from a set number (the starting psi when first initialized) or is variability between the tires? It didn’t seem like either of these applied unless all tires dropped a few psi’s in tandem. How small a deviation trips the warning? These questions aren’t addressed in the manual. BTW, does everyone know that a bicycle tire pump can easily be used to add tire pressure to your car? I asked because I did not know this until a few years ago. It saves trips to the gas station. Took about 70 pumps per tire to get from 30 to 35 psi. Cheers.
If your tire pressure is normal what sets them off is the batteries embedded inside of them are going dead... But that's probably not the case if you're talking about your 2022... And yes I use a larger size bike pump and can get tire pressure up to 45psi from low 30 psi in about 40 pumps. It's a great form of exercise when I'm done working on people's cars. Though I'd like to get my air compressor rebuilt.
When triggered for pressure (not battery or missing sensor), it should light up when any tire falls to a certain percent below its setpoint. For my Gen3 era, it is something around a 20 or 25% drop, others here should know the actual figure. A "TPMS Reset" will re-initialize the setpoint to whatever your tires currently have. Don't do this when the pressures are low, air them up first. Tire pressures normally change roughly 1 psi per 10 ℉ temperature change. Cold weather commonly triggers the warning if pressures have been allowed to sag for some time. Yes, several of us have been pointing this out for many years, though it seems to have few takers. Your bicycle pump must be small. My normal-sized 1" diameter floor pump, the same size as the local bike club uses for event support, needs only 7 strokes per 1 psi on my Gen3 Prius, or 35 strokes for a 5 psi increase. The same pump takes 10 strokes per 1 psi on my larger-tired Subaru. I have a larger diameter pump in the Subaru that takes fewer strokes, but requires significantly more handle force to reach the higher pressures used in my Prius. OK for my body size, but challenging for some smaller drivers. The usual bike pump is twice as fast as the 12V electric pump I used to use, with much less assault on the ears.
A corollary, don't do it at all unless you think the current setpoints are wrong. There's never a need to touch that button unless you want to change them. When you do, it will take whatever pressure is currently in the tires to be the pressure you normally want, and set the alarm thresholds about 25-ish percent below that. With a scan tool that shows TPMS data, you can see what the current pressures, temperatures, and setpoints are.
I’ve had one of these for almost 50 years, so they literally last a lifetime. A few years ago, I had to replace the hose/chuck due to dry rot, but everything else is going strong. In addition to simple top-ups when the weather first turns cold, the best use is when a tire goes down overnight due to a nail/screw. It will at least get you to the tire shop rather than having to put the spare tire on in the garage to be able to move the car.
That’s all I use now, simple and effective. On a few very rare occasions I’ve had TPMS warning, apparently for no valid reason, and went away. Tire pressures fine, maybe just some electronic “hand-shake” problem.
I had the TPMS warning for 2 months on my 2012 Plug-In and it just went away today??? Tire pressure was also fine when the TPMS lit up a few months ago.
