The 2500 Sprinters come with tire pressure monitors in all four wheels. They’re normally set for the recommended tire pressures, so if you’re driving an empty van and lower the pressure for a softer ride, the pressure monitor is likely to shout at you. Here’s how to calm it down.
70PSI is a really high pressure for an unloaded Sprinter. The ride gets a lot smoother if you lower the pressure a little, but the TPMS is likely to think this means your tires have a slow leak. The answer is to reset the TPMS so that it “learns” the new pressure values.
Note that this procedure only works for 2500-level vehicles. The 3500-level 6-wheel dual rear axle vehicles only come with aftermarket tire pressure monitor systems, so they are not covered here.
Here’s what the manual says about resetting the tire pressure monitor system (taken from the Mercedes 2016 manual).
When you restart the tire pressure monitor, the currently set tire pressures are taken as reference values for monitoring. In most cases, the tire pressure monitor detects the new reference values automatically, e.g. after you have: -- changed the tire pressure -- changed wheels or tires -- installed new wheels or tires However, you can also define reference values manually as described here. Before restarting the tire pressure monitor: -- Set the tire pressure to the value recommended on the Tire and Loading Information placard or the tire pressure table on the B-pillar on the driver's side. -- Make sure that the tire pressure is correct on all four wheels. Restarting the tire pressure monitor (vehicles without steering wheel buttons): -- Turn the key to position 2 in the ignition lock. -- Press the (M) menu button on the instrument cluster repeatedly until the display shows the following message: +CAL- TPMS -- Press the (+) button on the instrument cluster. The display shows: OK TPMS The tire pressure monitor activation process has begun. The tire pressures measured for the individual wheels are stored as the new reference values, provided that the tire pressure monitor considers them to be plausible. Restarting the tire pressure monitor (vehicles with steering wheel buttons): -- Turn the key to position 2 in the ignition lock. -- Press the Next or Previous Menu button on the steering wheel until the standard display appears in the display. -- Press the Up or Down Arrow button on the steering wheel repeatedly until the current pressure of the individual tires is displayed or the display shows the following message: Tire pres. displayed after driving for several minutes -- Press the (O) reset button on the instrument cluster. The display shows the following message: Monitor current tire pressure? -- Press the [+] button on the steering wheel. The display shows the following message: Tire pres. monitor reactivated The tire pressure monitor activation process has begun. The tire pressures measured for the individual wheels are stored as the new reference values, provided that the tire pressure monitor considers them to be plausible.
However, lots of people on the Sprinter forum report that this procedure doesn’t work for them. That’s because there are some other things you need to be aware of too.
More conditions you need to meet for TPMS resets to be successful
First, resetting the system might not be necessary if the change isn’t big. The learn-in process that happens every time you start driving may just take care of it.
If you do need to do a reset, there are several conditions that need to be met in order for the reset to work.
- The van must be driven at more than 16mph for at least 10 minutes after the reset (so the sensors “wake up” and start measuring the new pressures).
- This must be done within 20 minutes of the reset (otherwise the system “forgets” it’s been asked to reset).
- Tire pressures must not vary by more than 1.5psi during this time (don’t drive so fast that you heat the tires up a lot).
- The pressure difference between the four tires must be less than 22psi.
- The pressure in all four tires must be more than the NHTSA minimum pressure (which I think is 24.9psi for passenger vehicles – might be different for Sprinters).
TPMS warning types
It might be that you can’t do a reset because something really is wrong with the pressures of your tires, or you have a defective sensor. If you’re getting warnings, check the potential causes.
- Soft warning (lamp illuminates, or “Tire pres. Adjust pres.” message appears at end of trip) if the pressure reduces beyond the threshold set by the algorithm.
- Hard warning (“Check tires” message) if the pressure reduces beyond the additional lower threshold set by the algorithm, or if the pressure goes below the NHTSA fixed minimum pressure.
- Hard warning (“Warning Tire defect” message) if the pressure drops by more than 3.6psi per minute (compensated for temperature).
- Flashing warning lamp (flashes for about one minute, then stays illuminated, may start flashing only after you’ve been driving for a while), or “Tire pres. monitor inoperative” message – the TPMS system is malfunctioning.
Geeking out on TPMS details
Here is some more detail about the TPMS. Reading this might help you diagnose why the reset isn’t working for you.
The sensors in the wheels transmit tire pressure, tire air temperature, and acceleration (along with sensor ID, mode, & battery status). They run on either 315MHz or 433MHz. There’s an antenna at the front and the rear of the vehicle to capture the signals from the wheels. The antennae are boxes bolted to the underside of the chassis. These signals are sent to the control unit under the driver’s seat and from there to the instrument cluster.
If you use wifi or cellular equipment and it’s placed too close to the receivers, it might interfere and stop the sensor readings from being picked up. This will normally throw an error message on the dash.
Sensors enter “park mode” if they detect less than 5g acceleration for 15 minutes. In this mode they measure pressure every minute, but only transmit if the pressure goes below the lower limit. After 13 hours, they switch off entirely.
Sensors enter “drive mode” if they detect more than 5g acceleration for 20 seconds. At this point, they take a pressure reading every five seconds and transmit data every 15 seconds for around 9 minutes. This is called “learn in” mode. During this time, the system is making sure that the measurements from each sensor make sense.
After this time, if the vehicle is still moving (sensor acceleration is more than 5g), the sensors start transmitting every minute, or if the tire loses pressure to the lower limit. If the vehicle stops for more than 15 minutes, the sensors return to park mode.
Because tire pressures increase when you drive (the tire heats up, raising the pressure), the pressure sensor doesn’t just warn based on tire pressure alone, but on a combination of pressure and temperature.