I noticed a strange issue with my TPMS the other day. First, the front driver's side tire indicated low air pressure (29 psi). Oddly, the other tires were also at 29 psi, but not detected for low air pressure. So I put some air in the front left tire; 32 psi (now slightly more than the other tires). Yet the orange low pressure indicator for that tire did not go away.

The next day all four tires pulled a low air pressure signal with psi's in the low 30's.

I know those pressures are a little low, but I've seen the tire pressures jump to mid-30's and are still being considered "low" by the system.

I'll probably give the dealership a call some time this week, but I'm curious if anyone else came across this issue before.

 

Since you have an Aspec model, the correct pressure for your tires is 36 PSI according to the manual. (see image).

The low pressure alarm will not come on immediately if the pressure drops just 1 PSI, but it is designed to give a little flexibility due to changing temperatures throughout the day. When the pressure does get low enough (I feel that 30 PSI is quite low) the low pressure indicator will activate, but it will not go out again until the pressure is returned to a healthy 36 PSI.(within a 1-2 PSI range)

I feel that all your tires are moments away from showing a low tire pressure warning. The front left was slightly lower than the others and the first to create a warning. Set them all back to 36 PSI and all warnings will disappear.

EDIT I assume that you know that pressures will rise on warmer days and drop on cooler days. Pressures will also increase as the tire temperature rises during driving.. That is why you saw the changes from one day to the next.

 

Tire pressure is measured COLD which means basically the first thing in the morning, prior to driving on it , it should read 36 and go up from there. If it's 29/30 and GETS to 36 when hot, it's still "low"

 

TPMS sensors aren't the most accurate things in the world, the reason that the system is set to alert quite early. The TREAD Act requires that the system alerts at the latest when the pressure falls 25% and Acura tends to alert very early - usually at 15% or so.

If a car is designed for multiple tire sizes/pressures, the the system will most likely be "set" for the highest one whih is what? 37psi? That 15% would be 5-6psi, so you'll see an alert around 31/32psi - what you are seeing now.

 

Correct. For every 10 degrees variance in temps, the psi will go down/up by 1. For every month that goes by, a "good" tire will lose 1 psi, so between time and the drop in temps, that 5 or 6 psi loss is quite normal - assuming that tires were properly inflated to begin with.

 

Thanks for the input. Sounds like the thresholds for low air pressure warnings are just higher than what I'm used to seeing. ie my TL won't warn of low air pressure until 26-27 psi.

In another strange turn, my front driver's side is at 31 psi and went back to green, while the others remain in a warning state. Seems like things get a little inconsistent/finicky around that range.

As the weather is only getting colder I'll just bring them all back up to 36 psi.

 

I'd actually put about 38 or so in, because it'll just keep getting colder over the next few months. Also, make sure to check your tire pressures regularly - the car makes it easy to do.

 

Well that's because your TL's pressure was 32 so 26/27 sounds right.

This car's pressure is 36


Math..

 

Hello I had the same problem last week with 3 TPMS out of 4 in problem.
I have a RDX 2020 model A-SPEC.
All had 31 PSI of pressure per tire.

To fix it all, took her a short trip from Canada to the USA 800 Kilometers.

I did not change the air pressure in my tires. it is corrected alone.

It seems not very stable as a system, never experienced this problem with 3 Grand Cherokee and a Ford Edge.

 

your pressure is way too low. put a few lbs into it.

 

So what you experienced is because Acura built an "not very stable" system? What is it exactly that you find "not very stable".

Is it the fact that 3 of your tires showed low pressure with 31 PSI of pressure. Well that is exactly what should happen when the pressure is 5 PSI below the recommended setting (36 PSI for the Aspec). Nothing unstable here.

Is it the fact that only 3 of the 4 sensors showed low pressure warnings when they were all at the same 31 PSI. Due to slight variances in manufacturing precision, these sensors can vary slightly in both the pressure that they are indicating, and the pressure at which they indicate a low warning. You can be sure that the 4th tire was very close to indicating a low pressure warning at any moment. Although this isn't ideal, it is a fact of the manufacturing process, and certainly isn't unstable.

Is it the fact that the low pressure warnings went away after driving the car 800 KM. If you had read any of the previous posts you would have learned that pressure will increase as temperature increases. As you drove your RDX the tire temperature increased due to the flexing of the sidewall, and the contact with the pavement. In fact because your pressure was so low, the sidewall flexing would have been greater than normal, causing a rapid increase in tire temperature. If you had waited for a warmer day, the pressure would have also risen in the tires, and the warnings would have also gone away. This is one of the laws of physics, and the fact that it happens is not because of an unstable system,

Is it the fact that you never had a low tire pressure warning on your previous vehicles?. It sounds like you never let the pressure in your other vehicles get as low as this before. You may have have other vehicles with 31 PSI before that did not raise an alarm, but remember that the RDX did not raise the alarm because the pressure was 31 PSI, but because the pressure was 5 PSI below the proper value. If your Ford Edge had a recommended tire pressure of 32 PSI, you probably wouldn't get a warning unless the pressure dropped to 27 PSI. This isn't a sign of instability, this is working according to design.

If you haven't read the owners manual, you can also verify the proper tire pressure by looking at the sticker in the drivers door jamb. As I said before, the Aspec is suppose to be set at 36 PSI. These RDX's handle remarkably well when the tire pressure is set at the proper value. When your pressure is 5 PSI low, not only will you get abnormal tire wear, but the car will tend to sway when making steering corrections during high speed curves. For this reason I like to run my tires a few PSI above the recommendations to obtain more precise steering. I know that this makes the ride a little harsher, and can introduce abnormal tire wear as well, but handling is my priority, and is one of the reasons I chose the RDX.

I find it odd that vehicles are equipped with these modern warning systems, and when they actually warn the driver of a real problem, the driver complains about the system being wrong and never considers that he may really have low tire pressure..

 

That's just a silly comment


The TPMS system is working as designed. The reason it "self-adjusted" as you drove 800 km is because when you drive, the air in the tires are heated up and as such, pressure expands (PV = nRT for those who skipped chemistry class)


As suggested above, get your tire pressure to nominal pressure as outlined on the sticker on your door jamb (when the car is COLD), and then you won't have any issues.

 

had this issue pop up this morning - only the front right tire indicator blinking red while all the tires were at 30psi. Used the included air compressor to get them all back to 36 (aspec); problem solved. Note to others who might find this thread - my back right tire did NOT alert me when 36psi was reached. All other wheels would trigger beep/flash continuously for 5 seconds at 36, but the back right tire went all the way to 40 without triggering. Released air back down to 36 as measured by the middle screen on the dash (restart the car to get a new reading).

I think the car rides much more smoothly at 36 so shame on me for letting it get down to 30 haha.