3.2.2 CAN BU S
Th e CAN bu s (con t r oller a rea n et wor k ) is a da ta
bu s syst em specifica lly design for int er m odu le
comm u nica t ion on t h is veh icle. The CAN bus con-
sist s of a specia l t wist ed t wo-core ca ble. Con t rol
modu les are con n ect ed t o t his #twisted pair#.The
CAN bu s incor por a tes t wo t erm in a t in g r esist or s.
On e t er min at or is bu ilt in t o th e E n gin e Con t r ol
Module (E CM) a nd t he ot h er is bu ilt int o t h e Sen tr y
Key Rem ot e E n t ry Modu le (SKREE M). E a ch r esis-
tor ha s a va lue of 120 ohm s. The r esist or con dit ion
can be con fir m ed by discon n ectin g th e contr ol m od-
ule an d m ea su r in g t h e r esist a n ce va lu e at t h e
appr opr ia t e con tr ol m odu le pin s. Th is m ea su re-
men t sh ou ld r ea d 120 ohm s. Th e t wo CAN cir cu it s,
CAN C Bu s (+) an d CAN C Bu s (-), a r e br idged by
th ese t wo t er min at ing r esist or s wh en a ll con tr ol
modu les ar e con n ect ed to th e bu s. Th ese t wo resis-
tor s a r e con n ect ed to t he CAN bus n et wor k in
para llel. The measu rement between th e two
twist ed CAN cir cuit s, wit h bot h t h e E CM an d
SKRE E M connect ed, sh ou ld mea su r e a va lu e of 60
ohm s.
Th e CAN bu s is bi-dir ect ion a l. Th is m ea ns t h at
ea ch conn ect ed con tr ol modu le ca n sen d a nd receive
in for ma t ion . Tr a n sm ission of da ta t a k es pla ce re-
du nda n t ly via bot h cir cu it s. Th e da ta bus levels ar e
mir ror ed, m ea n in g t ha t if th e bin a r y level on on e
cir cu it is 0, the ot h er cir cu it t ra n sm it s bin a ry l evel
1 a n d vice ver sa . Th e t wo lin e con cept is u sed for
two rea son s: for fa u lt iden t ifica tion a n d as a sa fet y
concept .
If a volt a ge pea k occu r s on ju st on e cir cu it , t he
receiver s can iden t ify t his a s a fau lt an d ign or e th e
volt age pea k . If a sh ort cir cu it or in t err u pt ion
occur s on on e of th e two CAN cir cu it s, a soft wa r e-
ha r dwa re lin ked sa fet y con cept allows swit ch in g to
a sin gle-lin e oper a tion . Th e defect ive CAN cir cu it is
sh ut down. A specific da ta pr otocol con tr ols h ow a n d
wh en t he pa r ticipa nt s ca n sen d a n d receive.
NOTE: It is important to note the CAN Bus
circuits are used for inter-module
communication only, and is no way
connected to the K-Lines.
Th e followin g m odu les t h at u se th e CAN Bu s on
th is veh icle ar e:
• Aut om a tic Tem per at u re Con t rol (ATC)
• Con tr oller Ant ilock Br ake (CAB)
• En gin e Con tr ol Modu le (ECM)
• In st ru m en t Clu st er (IC)
• Sen tr y Key Rem ot e E nt r y Modu le (SKRE EM)
• Sh ift er Assem bly (SA)
• Tra nsm ission Con t rol Modu le (TCM)
3.3 HEATING & A/C SYSTEM
3.3.1 AUTOMATIC TEMPERATURE
CONTROL (ATC)
3.3.1. 1 S Y S T EM CON T R OL S
Th e ATC Modu le:
• is fu lly a ddr essa ble wit h t he DRBIII".
!
Th e DRBIII " commu n ica t es with t h e ATC
Module t h rou gh th e Dia gn ost ic Lin k Con n ect or
(DLC) via a K-Lin e.
• comm u n ica t es wit h ot her m odu les over t he Con -
tr oller Area Net wor k (CAN) C Bu s.
• cont r ols A/C clu tch oper a tion .
• cont r ols E BL oper at ion .
• cont r ols wa t er cycle va lve oper at ion .
!
Th e wa t er cycle va lve is a n orm a lly open va lve,
mea n in g th a t it a llows full en gin e coola n t flow
th r ough th e h ea ter core wh en no power is
deliver ed t o t he va lve. Th e ATC con t rols t h e
va lve wit h a pu lse widt h sign al. Th e lower t h e
percen t age of t h e pu lse widt h sign a l t he mor e
th e va lve is open .
• cont r ols Residu a l H ea t U t iliza t ion (RE ST) func-
tion .
• cont r ols blower m ot or oper a tion , pr ovidin g fou r
blower speeds (Low, M1, M2, & H igh ).
• cont r ols r ecircu la t ion a ir solen oid va lve.
• cont r ols t h e mode door via ca bles.
• cont r ols t h e m a in power su pply to the H ea t er
Booster (if equ ipped).
• uses a ir in let tem per at u r e sen sor, a ir ou tlet t em -
pera t ur e sen sor, an d eva por at or t emper a tu r e
sensor in pu t, a s well as da t a from ot h er modu les
to m a in t ain occu pa nt com for t levels.
3.3.1.2 SYSTEM DIAGNOSTICS
Fa u lt det ect ion is th r ough a ct ive a n d st ored Dia g-
nost ic Trou ble Codes (DTCs)
• DTCs a r e d isp la yed by t h e DRBII I".
• Active DTCs are t hose wh ich cu r ren t ly exist in
th e syst em . Th e condit ion ca u sing t h e fau lt mu st
be repa ir ed in or der t o clea r th is type of DTC.
• St ored DTCs a r e t h ose wh ich occu r red in t h e
syst em sin ce th e ATC Modu le r eceived the la st
#clea r dia gn ost ic in fo# message.
Testing Preparation & Diagnostics
Set t he n ecessa r y system funct ion s accor din gly so
th a t all of th e followin g pr er equ isit es ar e met prior
to per formin g dia gn ost ic t est s on th e ATC syst em:
5
GEN ERAL I N FORM AT I ON
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