TRW Automotive Electronics 14RC Benutzerhandbuch

Depending on the complexity of the system fitted, the tire pressure monitoring (TPM) system, 
consists of the following units: 

•  an electronic control unit (ECU) called 14RC 

•  four 29EC initiator units mounted in the wheel arches 

•  and four or five wheel sensors mounted in each of the tires. 

 
The system monitors the pressure and temperature within the tires and flags an alarm via an 
UHF radio link when the tire pressure falls below predetermined limits. The warning display 
forms part of the dashboard. 
 
Two types of system are available, termed high line and low line. In the low line system the 
29EC initiators are not fitted and the wheel sensors are factory fitted in active mode. In this 
application the sensors transmit data routinely every three minutes whether the vehicle is 
being driven or not. The high line system uses the initiators to transmit a low frequency signal 
to the wheel sensors – this activates them and this forces them to transmit. The highline 
system provides a faster update rate from the sensor and can provide an earlier warning of 
problems. 

 

2. Operation 
 
There are no user adjustable controls on the TPM system. All the information is 
communicated by the dashboard display. The display will have anywhere between two and 
six lamps depending on the vehicle model, these are TREAD (Transportation Recall 
Enhancement, Accountability and Documentation act) lamp, diagnostics lamp and four 
positional indicating lamps (identify actual wheel with the problem). The diagnostics lamp 
will light if there is a problem with the TPM system, the TREAD lamp typically comes on 
when any tire is 25% under inflated. When the TREAD lamp comes on, the user is expected 
to rectify the problem when it is safe to do so.