Tire Pressure Monitor - SMART Series 451 Service Manual

SN_Typ 451_us.book Seite 67 Freitag, 30. November 2007 1:56 13
General
The tire pressure monitoring system (TPM [RDK])
monitors the air pressure in the individual tires and
improves active safety. A previously stored tire pres-
sure is used as a comparative value. If a relevant loss
of pressure occurs, the tire pressure monitor
warning lamp in the instrument cluster warns the
driver. The tire pressure measuring range is p = 0 to
78 psi (p = 0 to 5.5 bar).
The TPM [RDK] system has the following subfunctions:
• Tire pressure sensing
• Warning display
• Manual restart
Function requirements
• Circuit 15 ON
• Tire pressure monitor (TPM [RDK]) system
functional
Tire pressure sensing
The TPM [RDK] control unit is permanently opera-
tional. Each time the CAN wakes up, the control unit
performs a re-initialization. While driving, the tire
pressure monitoring (TPM [RDK]) system continuously
monitors the tire pressure of all rotating wheels (with
circuit 15 OFF for a further t = 19 min). When the
vehicle is parked for t > 19 min, on-board wheel
detection and axle assignment must first be
completed via the TPM [RDK] wheel sensors. While
driving, the TPM [RDK] wheel sensors transmit data
telegrams every 60 seconds.
These data telegrams contain the following informa-
tion:
• Tire pressure
• Tire air temperature
• Individual serial number
• Status information
(manufacturer, direction of rotation, operating
mode etc.)
In addition the TPM [RDK] control unit takes into
account the outside temperature and the vehicle
speed for the tire pressure determination. These data
are provided via CAN by the instrument cluster.
Warning indicator
A warning is issued when a relevant loss of pressure
has been detected in at least one of the tires. The
warning is issued in the instrument cluster via the tire
pressure monitor warning lamp, but the specific tire
where pressure loss has occurred is not specified.
Manual restart
The tire pressure to be monitored can be reset via the
TPM [RDK] switch on the cockpit switch panel. When
the TPM [RDK] switch is pressed, the current tire
pressure is stored in the memory of the TPM [RDK]
control unit and is then used as the reference pres-
sure, as long as it is within the permissible limits.
The tire pressure monitor warning lamp in the instru-
ment cluster flashes to indicate that a manual restart
has taken place.
i Note
A manual restart must be performed each time the
tire inflation pressure is changed and when a
wheel, wheel sensor or the TPM [RDK] control unit
is replaced.
If the nut on the valve element of a wheel sensor is
loosened, all components of the valve element
must be replaced.
See the Workshop Information System (WIS) for
further instructions and information.
Introduction of the smart fortwo, Model Series 451

Tire pressure monitor

67