The cont rol ling software for t he TPMS i s located wi thi n t he CJB. The s oft ware det ects t he fol lowing:
t he ti re press ure is bel ow t he recommended low pres sure value - under infl ated t iret he pos i ti on of the t ire on t he vehi cle.
The s ys t em compri s es a Radio Frequency (RF) receiver, 4 init iat ors and 4 ti re press ure s ens ors (5 if t he spare wheel has as ens or fi tt ed).
The 4 i nit iators are hard wi red t o t he CJB. The i nit iators t rans mit 125 KHz Low Frequency (LF) s ignals t o t he t ire pres s ures ens ors which res pond by modifying t he mode s t at us wi thin the RF trans mi s si on. The 315 or 433 MHZ RF s ignals aredetected by the RF recei ver whi ch is l ocat ed at the rear of t he vehicle, behi nd t he headl ining. The RF receiver is connect edt o the CJB on the Local Interconnect Net work (LIN) bus . The received RF s i gnals from t he t ire pres s ure s ensors are pas s edt o the CJB on the LIN bus and contain identi fi cat ion, pres sure, temperat ure and accel erat ion i nformat ion for each wheeland t ire.
The TPMS s oft ware communi cat es wit h t he ins trument cl ust er via t he medium s peed Control ler Area Net work (CAN) bus toprovide t he driver wit h appropri at e warnings. The TPMS s oftware als o i ndi cat es s tat us or fail ure of t he TPMS orcomponents .
Tire Location and Identification
The TPMS can identi fy the pos it ion of t he wheel s on t he vehi cle and as s ign a recei ved ti re press ure s ens or identi fi cat ion t oa s peci fi c posi ti on on t he vehi cl e, for exampl e FL (front l eft ), FR (front ri ght ), RL (rear left ) and RR (rear right). Thi s feat ureis required because of the di fferent pres sure t argets and t hres hold bet ween the front and rear t ires.
The wheel l ocat ion i s performed aut omati cal ly by t he TPMS s oft ware us i ng an 'auto-locati on' funct ion. Thi s functi on is full yautomat ic and requi res no i nput from t he dri ver. The TPMS software automat icall y re-learns t he pos it ion of t he wheel s ont he vehi cl e if t he t ire pres s ure s ensors are replaced or the wheel posi ti ons on t he vehi cl e are changed.
The TPMS s oft ware can aut omat icall y detect, under all operati ng condit ions , the following:
one or more new t ire pres sure s ensors have been fit t edone or more ti re press ure s ens ors have s t opped t rans mi tt ingTPMS s oft ware can reject identi fi cat ions from ti re press ure sens ors whi ch do not belong to the vehiclet he spare wheel and one of t he 'runni ng' wheels on the vehicle have changed pos it ions .
If a new t ire pres s ure s ensor i s fi tt ed on any 'running' wheel , the s oft ware can learn t he new s ens or i dent ificati onautomat ically when the vehicle is driven for more t han 15 mi nut es at a s peed of more than 20 km/h (12.5 mph).
• NOTE: The s pare wheel is not fit ted wit h a t ire pres s ure s ens or.
TPMS Operation
Each ti me t he vehi cl e i s dri ven the TPMS s oft ware act ivates each i ni ti ator i n turn to t rans mit a LF 125 KHz s ignal t o eacht ire pres sure s ensor. The LF si gnal i s received by t he ti re pres sure s ens or which responds by t rans mit ti ng a 315 or 433MHZ (depending on market ) si gnal whi ch is received by t he RF recei ver. The si gnal contains coded data which corres pondst o s ens or identi fi cat ion, air pres s ure, air t emperature and accel erati on data. This i s t hen pas s ed to the CJB on the ISO9141 K Line.
If the vehicle has been parked for more than 15 minutes and t hen dri ven at a s peed of more t han 12.5 mph (20 km/h), t heini ti at ors each fire an LF s ignal in turn for 18 s econds i n t he fol lowing order:
Front LHFront RHRear RHRear LH.
Each ti re press ure s ens or res ponds i n t urn whi ch allows the TPMS s oftware to est ablis h the s ensor pos it ions at t he st art oft he drive cycle. This proces s is repeat ed up t o t hree t imes but l ess if t he s ens or pos i ti ons are already known. The processis known as 'Auto Locati on' and t akes 2 to 4 mi nut es t o compl ete.
Duri ng thi s peri od the t ire pres s ure sens ors t rans mi t at regular int ervals , once every 5 s econds (once every 15 s econds onNAS vehicles ). For the remainder of the drive cycl e t he t ire pres sure s ensors transmit once every 60 s econds or more oft enif a change of ti re pres sure is sens ed unti l the vehicle st ops and the TPMS ret urns t o t he parking mode.
Once the wheel pos it ions have been es t abl is hed, t he i ni ti ators s top t rans mit t ing t he LF s ignal and do not t rans mi t agai nunti l the vehicle has been parked for more than 15 minutes .
The warni ng appears in t he i ns t rument clus ter mes s age cent re when the i nfl at ion press ure has fal len t o 25% of t henominal pres s ure. The dis played mes sage wi ll als o i ncl ude the pos it ion(s) of t he affect ed wheel(s).
The TPMS enters 'Parki ng Mode' aft er the vehicl e s peed has been l es s t han 20 km/h (12.5 mph) for 15 minut es . In parkingmode t he t ire pres sure s ensors transmit a coded RF s ignal once every 13 hours. If t he ti re pres sure decreas es by more
t han 0.06 bar (1 lbf/in2 ), t he s ens or wil l trans mi t more oft en if pres s ure in t he t ire is bei ng los t.
The s pare wheel ti re press ure s ens or als o t rans mit s a si gnal once every 13 hours i n t he s ame manner as the 'running
wheels ' when in parki ng mode. If t he t ire pres sure decreases by more t han 0.06 bar (1 l bf/i n2 ), the s ensor wi ll t rans mitmore oft en if press ure in t he t ire is bei ng los t .
Initiators
