I was just driving and my tire pressure light came on but aren’t the values in the pic are what they are supposed to be? I’m pretty sure they were always between 45 and 47. Thanks for the help.

I believe the tire pressure you are seeing while accurate reflect the maximum tire pressure as per the sidewalls.

The correct tire pressure for your vehicle is found on your gas lid. I suspect it will be substantially less than 45/46 psi, more likely about 32/35 psi.

Once you reduce the tire pressure to the recommended psi, I think you will find your ride to be much, much smoother and better.

Hope this helps!

thanks for the reply. I purchased the car 7 months ago and it came out of the dealer with 47psi and it’s been like that ever since. Strange how the alert just came on out of no where

As above. Warning light means you have to lower to the correct values and reset the warning pressure.

Your alarm was probably set to 43 or 44 and a cold morning reduced the pressure enough to set it off.

I don't know why the dealers love to overinflate the tires. I guess it goes along with overinflated prices!

Many cars of all different brands sometimes are delivered to the customer with high tire pressure. Usually that is the tire pressure that they inflate the tires to truck the vehicle to the dealer from the factory or the port. A knowledgeable dealer will reduce the pressure to the suggested level before delivery and not leave it at the higher pressure. Or it simply could have been a mistake. My $0.02.

So the psi in the gas cap differs from what’s on the door jam. Which would you guys say is right?

It should be adjusted to the recommendation on the gas filler lid and reset in the dashboard.

In the app it says my tire pressure is low not high.

Use the gas lid which is specific for your car. The pressure on the door jam is "generic".

Many, many threads and post on this subject: Use the gas lid.

Hope this helps

The pressure you see on your display is the current pressures and your car is indicating all are over pressure. The gas lid is the proper values to use when setting cold tire pressure. Ignore the door jamb. Resetting the TPMS system will change the value the system expects to see. For example, mine are all at 37psi and that is what TPMS is set to as well. The TPMS has a tolerance and won't alert for small variances in pressure as the tires heat and cool. This is normal. When mine are hot, they go as high as 43psi and I never get an alert. To see cold pressure, go to that screen and drive at least a few thousand feet and they will start showing real-time pressure. Or you could just use a pressure guage and air compressor and set them to the proper cold psi based on your gas lid. In your case, you are too high, but your tires are hot so not really unexpected. They may just be over by 1-2 psi for the TPMS to alert. It may be just that your TPMS needs to be reset.

My advice. Set the pressure to the proper psi when cold, reset the TPMS system and you should be good.

If it's saying tires are too high when they are 118°F and 46psi (front) and 106°F and 45psi (rear) then I would expect that TPMS is saying they are low all the time. The pressure will go down when they cool. Your pressures are high, but not that high considered the temperature they show. More than likely someone over filled them and then reset TPMS. I recall you have 20" wheels which are the same as mine. I'm guessing your proper pressure is 37psi all around just like mine.

thank you for detailed reply. For some reason the notification I get through the app is that my pressure is low, but I have to assume that’s an error. My tires came out of dealer at 45psi but I’m now seeing that’s too high as my gas flap says 35-40 for my tire specs. I guess tomorrow I’ll let air out of the tires and reset the values. Thanks again.

yessir you are correct. I’m gonna set them to 37 then. Thanks pal.

it is reading as too low because the value was set too high. When you reset the value to the lower value, it won’t read as too low until you get to the same proportion or percent below that new value.

many of us due to the extreme inner tire wear that Mercedes has in many of their vehicles, use a slightly higher pressure, which also protects the wheels in urban driving. Funny enough and contrary to many peoples experiences when I recently had my car at the dealer, they lowered my pressures back down to the stock pressure…. i’m i. a different vehicle, but this is all the same for any of these vehicles in my opinion. With tires at low stock pressure, I’d destroy my wheels at the speeds I drive…

It was claimed that overflated tires help with prevent flat-spotting on delivery vessels and when sitting on the lot.

We pay top money for PDI, they should had done this. Sadly, chances are, PDI means you pay them to take the vehicle for a joyride (in some of my experiences).

Yesterday my TPMS light came on just like the OP's. In the service menu, all 4 tires had the yellow band around the tire and they all were 37 (one 36) PSI. My cold tire PSI on the gas lid says 36 which is what I set them to when cold. Problem was, the tires were hot and showed 37 with temps over 100°F. I figured I would too them off when it was cold. Took the car this afternoon, forgetting about the TPMS alert and with a mile the light came on. Tires showed 37 PSI and temps in the mid 90’s. Turned around, went home, fired up my compressor and topped them all to 39PSI. Drove about a mile and the PSI went from 37 to 38 and the light still didn't go off. I reset the TPMS and the light went off. It's been hot here. In the mid to upper 90's and in the garage it's even hotter. I'm going to wait until the night with the tires cool and set them all to 36 and then reset the TPMS. Thought it was strange that it reported a TPMS fault when they were within spec. I thought it was compensating for the temp but in my drive after setting them to 39 (based on my digital inflator) they never moved from 38 even though the tires went up to 102°.

Another strange thing is the CEL went on around the same time the TPMS light when first drove today. Car is running fine. But the CEL is still in and no warnings in the message center. Going to have MB do a remote diag in the morning, but thought it was strange to happen at the same time. Could be coincidence, but I'm not so sure. Drove to the store and back with the CEL on. No issues with the car otherwise.

Bingo ! Yesterday my TPMS lights came on too, for all 4 tires. For no ostensible reason, since the pressures are as normal as they have always been, for the past 7000+ miles. I have a feeling it is software related, and some kind of a glitch. I do not have the CEL however.

Since I ceramic coated the car, I am garaging it for the next one week for the coating to cure well, but would love to hear what your dealership says. Thank you.

Good luck with the remote diagnosis. I ask for it when my CEL came on and they said take it to the dealer. Would not check it remotely.

I set all 4 tires to 36 PSI this morning with the tires cold. Took it for a ride and all was normal and TPMS reported 36 PSI all around. They raised to 37 PSI after a 20 mile drive. CE light went out, but remote diagnostics said an software update is needed so car is going in on 9/1 for that and USB music fix.

My car has been parked, for the past few days, waiting for the ceramic coating to cure, and thus not sure if the TPMS situation has resolved by itself. But I will be driving the car tomorrow, since the ceramic coating should have fully cured by now.

Either way, I don't think my car's software is set for automatic updates and thus wondering what triggered all 4 tires (with normal pressures), to suddenly light up on the screen with the TPMS warning. Just like your situation, a few 1000 miles away from where I am. For whatever reason, I suspect it is some kind of a software update that caused this, if I were to take a wild guess.

If it's a software then it updated in stealth mode. I have auto update disabled and require a PIN to perform an update. I've not done an update in several months. I think it lost its reference data somehow. I reset TPMS and all has been fine since.

I just did a spin around the block (here in Phoenix, AZ), and the damn thing is still there. I guess I will need to do the software update at the dealer and get this sorted out.

Just reset your TPMS. While in that screen, hit the OK button on the steering wheel. It will pop up a menu with one option to reset TPMS to current values. This assumes the current pressures are what your ideal pressure is. If not. Adjust your pressures before doing this.

Thank you. That did the trick. I just took a quick spin after the reset, and things look good.