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According to this, it should be picked up from the settings in your car...have you verified those settings are correct ?
To switch the units for the "Hey Mercedes" voice response (and other MBUX displays), you will need to adjust the settings in the multimedia system manually . The voice assistant pulls information from the vehicle's set display units.
Steps to Change Display Units
Go to the Home screen on your MBUX infotainment display.
Scroll across to the "Settings" page or icon.
Select "System".
Scroll down and select "Display" or "Display messages". The exact menu names may vary slightly by model year and software version.
Look for "Units" in the display settings menu.
Select the desired unit (e.g., kilometers or miles, Fahrenheit or Celsius, kPa or bar/psi for tire pressure) depending on what specific response you are trying to change.
The system should immediately change the display and voice responses to the newly selected units.
I also noticed that the mountain heights shown on the navigation route are in meters not feet. My settings are correct for USA but nav won’t indicate correctly.
Mercedes doesn't allow you to adjust any units other than distance. The units for pressure and temperature are predetermined by the car's region. So for the USA the pressures should be in psi and temperatures in Fahrenheit. Some of the third-party coders have claimed that they can change it. Pressure in kg anything isn't used anywhere. Europe and much of the rest of the world uses kPa or bar. kg per square centimeter is a deprecated unit of measure and I've never seen it used anywhere. What exactly is it readying out? Pressure in kg isn't a correct unit. Is it reading them out in kg per square inch, or what exactly is it saying? When you bring up the tire pressure on the display, what unit are they in? As said, in the USA it should be psi. Sounds like this is another one of the wonderful bugs that have enriched MBUX since its debut.
Mercedes doesn't allow you to adjust any units other than distance. The units for pressure and temperature are predetermined by the car's region. So for the USA the pressures should be in psi and temperatures in Fahrenheit. Some of the third-party coders have claimed that they can change it. Pressure in kg anything isn't used anywhere. Europe and much of the rest of the world uses kPa or bar. kg per square centimeter is a deprecated unit of measure and I've never seen it used anywhere. What exactly is it readying out? Pressure in kg isn't a correct unit. Is it reading them out in kg per square inch, or what exactly is it saying? When you bring up the tire pressure on the display, what unit are they in? As said, in the USA it should be psi. Sounds like this is another one of the wonderful bugs that have enriched MBUX since its debut.
Yes, the voice is reading the pressure out in kPa. The readout if I keep scrolling under service (on the steering wheel) is in PSI. Very strange. It's much easier to ask Hey Mercedes what the tire pressure is rather than scrolling. I am able to ask in my BMW and it reads it out in psi.
Yes, the voice is reading the pressure out in kPa. The readout if I keep scrolling under service (on the steering wheel) is in PSI. Very strange. It's much easier to ask Hey Mercedes what the tire pressure is rather than scrolling. I am able to ask in my BMW and it reads it out in psi.
Sounds like a bug then. Somebody forgot to make Hey Mercedes properly aware of the car's region, or possibly something got miscoded in your car at the factory. Maybe somebody else can try it to see if they get the same. Just out of curiosity, if you explicitly ask Hey Mercedes to give you the pressures in psi, is it capable of converting them on the fly? FWIW, I generally have the pressures up in my instrument cluster at all times. In my '19 C63 there's a performance display that shows all the temps and the tire pressures. I primarily keep an eye on the temperatures, so I can judge the grip of the tires and know when the engine and transmission are warmed up. I don't remember from the top of my head if there's a similar display that you can bring up in the newer instrument clusters. They are less customizable than before.
Last edited by superswiss; Dec 1, 2025 at 12:11 PM.
Just wanted to chime in here that i am facing the same issue with my glc 350e. Oddly enough this happen after my car successfully upgraded to mBux 3.3 couple weeks back. Prior to the software update, I happened to get a low tire pressure light during my drive and I asked "hey mercedes" repeatedly what my tire pressure was. Each time, answer was in PSI.
Now after the update, when i asked for tire pressure, it is read in kpa only. I checked and confirmed my units in display only show ft and/or miles but no tire pressure setting. In my dash for service view, it lists my tire pressure in psi.
I've been trying to find others who may have noticed this same issue happening and this is the only post ive seen acknowledging this issue. I am based in California so it makes no sense why my units changed but only when i asked via hey mercedes
The Mercedes App, unit section, of your profile allows you to select kPa, bar, or PSI for tire pressures. I don’t know if that will change the Hey Mercedes read out though. I haven’t tried it yet.
Last edited by BenzC400; Dec 16, 2025 at 07:45 PM.
The Mercedes App, unit section, of your profile allows you to select kPa, bar, or PSI for tire pressures. I don’t know if that will change the Hey Mercedes read out though. I haven’t tried it yet.
I went into the app but did not see where to change the measurements.
I went into the app but did not see where to change the measurements.
Tap on the profile icon in the upper right corner, then Settings|Units, but those only apply to the app itself in my experience. For example I have temperatures set to Celsius in the app, but the car still shows Fahrenheit. So these settings do not apply to the car.
2025 E450 All Terrain Wagon, Nautical Blue Metallic, Macchiato Beige/Black Interior
Must be a bug. I'm in the same boat with my W214 E450 Wagon in the U.S. Prior to the 333 update I would use Hey Mercedes to check tire pressures and it would answer in psi. After the update it's been answering in kPa. On the service screen it reports in psi. The setting in the Mercedes app says psi. When I use Hey Mercedes and specifically ask for tire pressures in psi, it still responds with kPa. There's no place in the car's Settings menu that references tire pressure units - just Kilometers v. Miles and Fº v. Cº.
Looks like we will have to wait it out. I won't go to the dealer for it, but if I'm in for something else I'll mention it. I'm sure they'll look at me like I have 3 heads.
Tap on the profile icon in the upper right corner, then Settings|Units, but those only apply to the app itself in my experience. For example I have temperatures set to Celsius in the app, but the car still shows Fahrenheit. So these settings do not apply to the car.
Must be a bug. I'm in the same boat with my W214 E450 Wagon in the U.S. Prior to the 333 update I would use Hey Mercedes to check tire pressures and it would answer in psi. After the update it's been answering in kPa. On the service screen it reports in psi. The setting in the Mercedes app says psi. When I use Hey Mercedes and specifically ask for tire pressures in psi, it still responds with kPa. There's no place in the car's Settings menu that references tire pressure units - just Kilometers v. Miles and Fº v. Cº.
Looks like we will have to wait it out. I won't go to the dealer for it, but if I'm in for something else I'll mention it. I'm sure they'll look at me like I have 3 heads.
I agree it does appear to be a bug as everything you wrote above on your E450 is exactly verbatim to the same issue i've seen in my glc 350e. I did also check my mercedes app to confirm it says psi and it never changed. But just to test it out further, i even selected kpa in the app and let it save, then go back to psi and save. But hey mercedes doesn't seem to register that point and still say kPa.
This is my first mercedes and first mbux update...do they push out like a bug fix software update like a mbux 3.3.1 or something? Or we have to wait until mbux 3.4?
Noticed the same thing in my 2025 GLC after the software update with no joy in finding a way to reset it. I'll bring it up when I'm next at the dealer. BTW, I was impressed when (as I was driving) I asked "Hey Mercedes" to convert 240 kilopascals to psi and it gave me the correct answer.
Took my GLC 300 in for Service A last week and asked about the tire pressure audio reporting. It is a known issue and there is currently no interface that allows this setting to be changed. I anticipate MB will either add such an interface or - more likely - flip this setting to PSI for US spec cars in the next update that touches the code that includes this setting.
2025 E450.
Same problem.
Hey Mercedes gave it in psi until a software update.
Now in kPa.
I'm in Toronto and dealer can't find the problem.
Originally Posted by mjastuart
Took my GLC 300 in for Service A last week and asked about the tire pressure audio reporting. It is a known issue and there is currently no interface that allows this setting to be changed. I anticipate MB will either add such an interface or - more likely - flip this setting to PSI for US spec cars in the next update that touches the code that includes this setting.
2026 E 350 in Toronto, Canada. Same issue will either use the forum members' recommendations of converting or just using the phone app to check tire pressures for now.
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