Tire pressure monitor (TPM), activation - GF40.15-P-0001-02TR
In the event of the driver changing the air pressure, in the event of exchanging a wheel or changing a tire, the adjusted air pressure values must be stored in the TPM [RDK] control unit (N88) as specified monitoring values.
The filling pressure to be monitored can be manually determined by the driver by "reactivation" of the tire pressure monitor via the operating menu in the instrument cluster (A1). The temperature-compensated pressure thresholds for the warnings are set based on the pressure values at the time of reactivation. Manual reactivation is only planned as a stopgap solution in critical cases where automatic filling detection fails. Under normal circumstances (wheel exchange or driver sets new pressure values) new specified values are automatically determined by the filling detection function.
Reaction of the TPM [RDK] control unit after manual reactivation
If the tire pressure values are plausible to the TPM [RDK] control unit, both individually and in relation to each other, and over the minimum pressure specified for the model series, reactivation is carried out. The operating acknowledgement "Tire pressure monitor reactivated" is immediately shown. The current tire pressures are accepted as specified values on an axle by axle basis.
On vehicles with code (494) USA version, it is only possible to reactivate the TPM system manually.
Conditions for the acceptance of current pressure values as new specified values:
- Pressure values screened for 3 minutes
- On-board wheel detection completed
- Plausibility check on pressure values carried out
- Determination of specified values carried out after a positive plausibility check
Conditions for reinitialization of filling detection:
- Engine switched back on after more than 3 min idle time
- TPM wheel sensor signals a pressure change when vehicle is stopped
- New on-board wheels detected after start of trip
Requirements 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 minimum pressure specified for the model series
Description of operation
The TPM system is permanently operational is not actively controlled by the driver. Each time the CAN-B (Controller Area Network bus class B (interior)) is alerted by the starting procedure or ignition "ON", the TPM [RDK] control unit performs a reinitialization and starts to transmit messages to the instrument cluster. Reactivation of the TPM system can be initiated via the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111) on the multifunction steering wheel and the instrument illumination rheostat and reset button (A1r1) on the instrument cluster.
The TPM system can be reactivated in the following cases:
- After tire pressure change (e.g. from refilling)
- After every wheel or tire change
- After fitting new wheels or tires
When the TPM system is reactivated filling detection is also restarted.
System message (request to activate system)
Reactivate tire pressure monitor:
- Correct the air pressure at each wheel
- Switch on the ignition (circuit 15 "ON")
- Select the standard display with the system selection button (S110s3)
- Use the scroll forward/back button to select the TPM system
System message (information message)
The following message appears:
- After starting the engine
- If the vehicle is parked for more than 20 minutes
- If the vehicle is driven faster than 25 km/h
Reactivate tire pressure monitor
Press the instrument illumination rheostat and reset button.
The display changes to the selection screen with preselection "no". Press the + and - buttons for setting specific functions and volume control on the multifunction steering wheel. The selection screen with selection "yes" appears for approx. 2 seconds and then changes immediately to the confirmation screen.
Reactivation of tire pressure monitor carried out
From this point on the TPM system monitors the (re) set air pressure values of all rotating wheels. The TPM system has stored the current tire pressure as a new reference value.
All other buttons cause the activation sequence to be aborted.