Mercedes-Benz W211 models utilize an electronic system to monitor the pressure in your tires. This is due to regulations by the US government and updated safety standards.
The tire pressure information is used to notify you of a low tire pressure condition. If a tire loses pressure, a warning lamp is illuminated in the instrument cluster and a warning chime sounds. This is a very helpful system. If you have a tire puncture and are losing air, you will be notified, therefore allowing you to immediately pull over and reduce the damage to the tire. Any time you have a warning message related to tire pressure, immediately pull over and check all four tire pressures. If you had a low tire and repaired the problem, you will have to reset the tire pressure monitoring system. This can be done easily through your driver information menu located in the instrument cluster.
When checking air pressure, always use a plastic valve stem cap. A metal one can seize onto the TPM sensor and damage it. This applies to TPMS sensor equipped vehicles.
TPMS sensor battery life is approximately 7 years, the battery is not serviceable. With each data transmission, the sensor reports on remaining battery life to the control module. Battery life status can be checked using a Mercedes-Benz scan tool. When replacing a sensor, always use a new valve for your region. US sensors use a frequency of 315 MHz. Each sensor has a unique, wheel electronic identification number that it sends to the TPC module with each data transmission. The TPC module is programmed with this number to relate it with a specific wheel position on the vehicle. The wheel electronic identification number is stamped on the sensor. To program sensor location, you can use a Mercedes-Benz scan tool. Or, a slower method of learning is to simply perform an activation. While driving, first the wheel sensor locations will be learned and then the new pressure specifications will be stored. TPC will have to determine sensor location by measuring field strength at the antennas. TPC must receive a greater number of clear signals from each sensor
The TPMS sensor broadcasts a signal received by an antenna in the wheel well. That signal is then sent to the TPC control module and onto the instrument cluster.
You will have to activate the TPMS sensors when any of the following apply:
- Setting a different inflation pressure base-line value
- Cluster says to "re-activate TPC"
- Tires are rotated
- Winter tires are mounted
- A wheel sensor has been replaced
- The TPC control module has been replaced
- A TPC fault code has been erased
Activation is initiated using steering wheel & ICM buttons and completed by driving the vehicle. See procedure below.
Some warning messages and possible causes:
Tire pressure LF / check tire
- Pressure in one or more tires has dropped to 0.4 bar (5.8 psi) below the stored pressure
- Specific tire may not be indicated Message displayed continuously
Operation Warnings Displayed in RED: Tire Pressure LF / Caution Tire Defect
- Pressure loss >0.2 bar (2.9 psi) per minute
- Specific tire location indicated
- Stop immediately and install spare wheel / tire
Operation Warnings: Tire pressure / check tire
- Pressure in one or more tires dropped >0.2 bar (2.9 psi) below stored pressure. Message shows for 30 sec. After every start-up
- Pressure difference >0.4 bar (5.8 psi) between tires on same axle
- Pressures too low, temperature OK (<120 degrees C)
- After an activation request with implausible pressure adjustment
Function Warnings: Tire pressure monitor / Visit workshop
- CAN, component, sensor battery, DTC is stored
- Tire pressure monitor temporarily inactive
- During initialization, external interference, temp. >120 degrees C, additional wheel sensors in vehicle
- Tire pressure monitor activated
- During activation - pressures show after driving a few minutes
- Tire pressure monitor / Reactivate
- Pressure is 0.3 bar above stored value, or after replacing N88
A solid aluminum stem (red arrow) that has a nut on the base is a TPM sensor system. When checking air pressure, always use a plastic valve stem cap. A metal one can seize onto the TPM sensor and damage it. This applies to TPMS sensor equipped vehicles (green arrow).
Tire pressure information for your vehicle is located in the left side door jamb on the label (red arrow) shown in this photo.
Checking tire pressure: Call up the odometer display by pressing steering wheel buttons (green arrow). Display tire pressure by pressing steering wheel arrow buttons (yellow arrow). Four tire pressure values are displayed, illustrating each corner of the vehicle. Values will be displayed in either BAR or PSI. Blank pressure reading indicate that no values are stored.
Resetting the tire pressure system: Read the entire procedure before beginning. Once read, it will be easier to follow the steps. Tire pressures set correctly. Engine OFF / Ignition ON. Use steering wheel buttons (green arrow) to scroll to 0 mph display. Use steering wheel buttons ( arrow up/arrow down) to display tire pressure screen (blue arrow).
Resetting the tire pressure system: Screen will direct you to reset system using R button (green arrow). Tap the reset button (red arrow). Activation now begins. After driving 10-30 minutes, display will suddenly show four actual pressures. If the values you are trying to set are implausible, cluster will display:
tire pressure / check tire TPC.