Tire pressure monitor (RDK) activation - GF40.15-P-0001-02SXU

The tire pressure monitor (TPM) assists the driver with the permanent check of the correct tire inflation pressure.

The TPM system is reactivated in the following cases: 

• after a tire pressure change (e.g. by refilling)
• After each wheel or tire change
• after assembling new wheels or tires

The adjusted air pressure values in the TPM [RDK] control unit (N88) are stored as specified monitoring values.

The tire filling pressure to be monitored is determined by the driver manually by "Reactivating" the tire pressure monitor via the operating menu in the multifunction display. The temperature-compensated pressure thresholds for the warnings are established by means of pressure values at the instant of reactivation.

Description of operation 

The TPM system is permanently operational and is not operated actively by the driver. Each time the interior CAN is woken up by the starting procedure or ignition "On" (terminal 15) the TPM [RDK] control unit carries out a reinitialization and starts to transmit messages to the instrument cluster (A1).

Condition: adopting current pressure values as new specified values: 

• Pressure values filtered for 3 minutes
• Detection of the wheel in question awaited
• Plausibility check of pressure values carried out
• Determination of specified pressure values carried out after a positive plausibility check

Conditions for reinitializing filling detection: 

• Engine switched back on after more than 3 min idle time
• TPM wheel sensor reports a pressure change when the vehicle is stationary
• New wheels on the vehicle in question found after the start of the journey

Conditions for filling detection: 

• Filling detection started
• No pressure change (temperature compensated) of more than 0.1 bar (max/min value comparison) within monitoring period
• Tire pressures are above the minimum pressure specific to the model serial productions

Manual reactivation 

A reactivation of the TPM system is reactivated via the left multifunction steering wheel button group (S110). If the pressure values of the tires are plausible for the TPM [RDK] control unit both individually and in relation to each other and are above the minimum pressure specific to the model serial productions, the reactivation is carried out. A feedback "Tire pressure monitor reactivated" takes place. The current tire pressures are taken over as specified values on an axle by axle basis.

Filling detection is also restarted during manual activation of the TPM system.

Start manual reactivation: 

• Adjust tire pressure correctly in each wheel
• Ignition "On" (circuit 15)
• Use the system selection button to select the "Service" menu
• Use the scroll forward/back button to select tire pressure
• Confirm with OK button

The current tire pressure of the individual wheels appears or the message "Tire pressure display appears after driving for a few minutes" appears. The message: "Adopt current pressures as guidance value. Confirm with OK" appears.

System message after adopting the pressures as new guidance values, shown on model 221 up to 31.8.06 

Concluding system message, shown on model 221 up to 31.8.06 

The current tire pressures are adopted as guidance values after driving for a few minutes.

System message with tire pressure monitor running, shown on model 221 up to 31.8.06 

As of this instant the TPM system monitors the (newly) adjusted air pressure values of all rotating wheels. The TPM system has stored the current tire pressure as a new reference value.