Hey all - 2024 EAS 450+ with about 8,000 miles on it. No issues at all until this recent issue with the tire pressure monitoring system. I get a warning to correct tire pressure - which is actually fine. I reset the tire pressure monitor to use the current values as the new reference values which eliminates the warning. But then - once the pressure varies by 1 or 2psi in either direction, the warning comes back. So - a few minutes of highway driving which increases the tire pressure by 1 or 2psi brings the warning back. Same thing if it sits overnight and the tires cool. Have had many MB cars with this same system and have not seen this type of behavior. I hate to go to the dealer for something so minor, but I hate driving a car with the tire pressure warning on all the time. Any ideas?

 

Something wrong there. What is the exact pressure you are inflating your tires to? There usually is a hard coded lowest pressure level and the target pressure set by the TPMS reset. Your set level must be above the hard coded level in which case you should never get a warning when the pressure increases (tires heating up from driving). No idea really what could cause it, doesn't sound like a misbehaving sensor.

If you reset TPMS when tires are at about ambient temperature, cooling down overnight should neither trigger any warning.

 

Inflate the tires when cold to the correct level as documented on the spec sheet for the car. If you have trouble after that, next would be to look at what you are using to measure the tire pressure. Is it really that accurate a gauge? You may be under inflating without realizing it. Last would be to go to a tire shop and have them check the TPS sensors in the wheels. The batteries usually last seven to ten years, but it could fail (or the unit could fail) sooner.

 

@Lanzz ,

That's a frustrating issue, and a very unusual one for these cars. The other members have provided the excellent foundational advice—checking the pressure cold against the door jamb sticker is always the right first step.

However, your specific problem, where the warning triggers on both a 1-2 psi increase and decrease, points to a more nuanced issue that is common on these vehicles. It's likely not a faulty sensor, but a conflict between the car's two different sets of tire pressure recommendations.

Here's the deep dive on what's likely happening:

The "Two Sticker" Paradox

On these cars, Mercedes provides two different inflation standards, and they serve two different purposes:

1. The "Normal Load" Sticker (The Legal Requirement): This is the main placard on the driver's door jamb. It lists the pressures required to safely carry the vehicle's maximum load. Think of this as the Safety Standard.
2. The "Comfort" Sticker (The Mercedes Recommendation): This is often on the same placard or inside the charge port door and lists a lower PSI for a softer, more luxurious ride under a light load (e.g., just the driver). This is the Experience Standard.

The Root of Your Problem: You have likely, and logically, set your TPMS reference point to the lower "Comfort" pressure for a better ride. However, the car's computer has a hard-coded safety minimum that is based on the higher "Normal Load" pressure. This creates a tiny operational window where a 1-2 PSI change from normal driving (tires heating up) or cooling down overnight is enough to trigger a nuisance warning. The system is fighting itself.

The Definitive Solution: The J_Boxer TPMS Accuracy Test

To confirm this and get it fixed, here is a clinical method to use.

1. Go to any Mercedes-Benz service drive. They will do a complimentary tire pressure adjustment.
2. Provide a Specific Target. Before they touch the car, pull up your TPMS screen. Tell the technician, "Please set all four tires to precisely 41 PSI" (or whatever your higher "Normal Load" pressure is).
3. The Direct Comparison: Have them use their professional, calibrated gauge to hit that exact number.
4. The Immediate Verification: Before driving away, check your TPMS screen again. If you asked for 41 PSI but your screen now reads "38 PSI" on one tire and "41 PSI" on the others, you have definitive, unimpeachable proof that the sensor on that specific wheel is faulty or out of calibration.

This transforms your service visit from a vague complaint into a documented, verifiable warranty claim.

Hope this deeper dissection helps you get to the bottom of it.

 

Yes, I have run into this problem myself. Always inflate to the legal inflation amount, ignore the "comfort" recommendations. Your fuel economy (or electrical efficiency) will be higher at the legal settings too.

 

This deep dive into the "Two Sticker Paradox" and TPMS diagnostics brings up a final, more philosophical question that every owner eventually faces: the conflict between the manufacturer's Safety Standard and the expected Luxury Experience.

I have a personal case study that perfectly illustrates this.

Recently, I was preparing for a 12-hour road trip to Florida. The car was fully loaded—overloaded, really—with passengers and luggage. Following protocol, I inflated the tires precisely to the higher "Normal Load" pressure recommended on the door jamb placard for a vehicle at its GVWR.

The result for the first five hours of the trip was, to be candid, an unacceptably uncomfortable ride. The higher pressure made the suspension feel harsh, transmitting every minor road imperfection directly into the cabin. It completely destroyed the "magic carpet" feel that is the hallmark of this car.

So, I made a conscious, calculated decision. I pulled over and lowered the rear tire pressure by a few PSI.

The result was an immediate and considerable improvement in ride comfort, which made the remainder of the trip vastly more enjoyable.

Now, let's be clear: was this a potential compromise on the absolute letter of the safety guidelines for a vehicle at maximum load? Yes. Was it a necessary adjustment to restore the inherent nature of the luxury car I had purchased? Also yes.

This gets to the very heart of the ownership experience. The specifications on the door jamb are not just numbers; they are the bookends of an engineering trade-off. One end provides maximum load-bearing safety, and the other provides maximum comfort. The true art of owning these vehicles is understanding this trade-off and knowing how to make an informed, real-world decision based on the conditions.

The car is engineered to be both safe and luxurious. Sometimes, as the owner, you have to be the one to decide which of those two perfectly engineered characteristics gets priority on any given journey.

 

Hey, thanks everyone. I increased the tire pressure to 41lbs for front and 44lbs for rear and the light went out and has not come back on in the past 24 hours. The sticker on the door said cold inflation of 41lbs and 48lbs - so, I stopped short of the 48lbs in the rear in a small nod to ride quality. Appreciate your insight.