Table of Contents
Advertisement
t h e pr essu r e con st a n t . On veh icles wh ich a r e
equ ipped wit h a t r a ct ion con t r ol syst em , t h er e a r e
fou r a ddit ion a l va lves, t wo isola t e t h e m a st er cylin -
der a n d t wo sh u t t le. Du r in g a t r a ct ion con t r ol even t
t h e br a kes a r e a pplied t o r edu ce wh eel slippa ge.
P u m p Mo to r As s e m bly : Th e pu m p m ot or a s-
sem bly pr ovides t h e ext r a a m ou n t of flu id n eeded
du r in g a n t ilock br a kin g. Th e pu m p is su pplied flu id
t h a t is r elea sed t o t h e a ccu m u la t or s wh en t h e ou t let
va lve is open ed du r in g a n a n t ilock st op. Th e pu m p
is a lso u sed t o dr a in t h e a ccu m u la t or cir cu it s a ft er
t h e a n t ilock st op is com plet e. Th e pu m p is oper a t ed
by a n in t egr a l elect r ic m ot or. Th is m ot or is con -
t r olled by t h e ABM. Th e ABM m a y t u r n on t h e
pu m p m ot or wh en a n a n t ilock st op is det ect ed. Th e
pu m p con t in u es t o r u n du r in g t h e a n t ilock st op a n d
is t u r n ed off a ft er t h e st op is com plet e. Un der som e
con dit ion s, t h e pu m p m ot or will r u n t o dr a in t h e
a ccu m u la t or s du r in g t h e n ext dr ive off. Th e ABM
m on it or s t h e pu m p m ot or oper a t ion in t er n a lly.
3.3.4 ABS SWITCHES/SENSORS
Ma s te r Cy lin d e r: Th e m a st er cylin der is a st a n -
da r d t a n dem com pen sa t in g por t design for ABS a n d
n on ABS syst em s. Tr a ct ion con t r ol veh icles u se a
du a l cen t er por t m a st er cylin der. F or pr oper t r a c-
t ion con t r ol oper a t ion t h e st a n da r d m a st er cylin der
m u st n ot be u sed.
A flu id level swit ch is loca t ed in t h e m a st er
cylin der flu id r eser voir. Th e swit ch closes wh en a
low flu id level is det ect ed. Th e flu id level swit ch
t u r n s on t h e br a ke wa r n in g in dica t or by gr ou n din g
t h e in dica t or cir cu it . Th is swit ch does n ot disa ble
t h e ABS syst em .
Wh e e l S p e e d S e n s o rs a n d To n e Wh e e ls : On e
a ct ive wh eel speed sen sor (WSS) is loca t ed a t ea ch
wh eel. Th e sen sor s u se a n elect r on ic pr in ciple
kn own a s m a gn et o-r esist ive t o h elp in cr ea se per for-
m a n ce, du r a bilit y a n d low speed a ccu r a cy. Th e
sen sor s con ver t wh eel speed in t o a sm a ll digit a l
sign a l. A t oot h ed gea r t on e wh eel ser ves a s t h e
t r igger m ech a n ism for ea ch sen sor.
Th e ABM sen ds 12 volt s t o power a n In t egr a t ed
Cir cu it (IC) in t h e sen sor. Th e IC su pplies a con -
st a n t 7 m A sign a l t o t h e ABM. Th e r ela t ion sh ip of
t h e t oot h on t h e t on e wh eel t o t h e per m a n en t
m a gn et in t h e sen sor, sign a ls t h e IC of t h e sen sor t o
t oggle a secon d 7 m A power su pply on or off. Th e
ou t pu t of t h e sen sor, sen t t o t h e ABM, is a DC
volt a ge sign a l wit h ch a n gin g volt a ge a n d cu r r en t
levels. Th e ABM m on it or s t h e ch a n gin g a m per a ge
(digit a l sign a l) fr om ea ch wh eel speed sen sor. Th e
r esu lt in g sign a l is in t er pr et ed by t h e ABM a s t h e
wh eel speed.
B e c a u s e o f in te rn a l c irc u itry, c o rre c t w h e e l
s p e e d s e n s o r fu n c tio n c a n n o t be d e te rm in e d
by a c o n tin u ity o r re s is ta n c e c h e c k th ro u g h
th e s e n s o r.
GEN ERAL I N FORM AT I ON
Cor r ect a n t ilock syst em oper a t ion is depen den t
on t on e wh eel speed sign a ls fr om t h e wh eel speed
sen sor s. Th e veh icle's wh eels a n d t ir es sh ou ld a ll be
t h e sa m e size a n d t ype t o gen er a t e a ccu r a t e sign a ls.
In a ddit ion , t h e t ir es sh ou ld be in fla t ed t o t h e
r ecom m en ded pr essu r e for opt im u m syst em oper a -
t ion . Va r ia t ion in wh eel a n d t ir e size or sign ifica n t
va r ia t ion s in in fla t ion pr essu r e ca n pr odu ce in a ccu -
r a t e wh eel speed sign a ls; h owever, t h e syst em will
con t in u e t o fu n ct ion wh en u sin g t h e cor r ect fa ct or y
m in i-spa r e.
3.3.5 ABS INITIALIZA TION
Syst em in it ia liza t ion st a r t s wh en t h e key is
t u r n ed t o "r u n ". At t h is poin t , t h e ABM per for m s a
com plet e self-ch eck of a ll elect r ica l com pon en t s in
t h e a n t ilock syst em s.
Bet ween 8-17 km /h (5-10 m ph ), a dyn a m ic t est is
per for m ed. Th is will m om en t a r ily cycle t h e in let
a n d ou t let va lves, ch eck wh eel speed sen sor cir-
cu it r y, a n d r u n t h e pu m p m ot or a t 25 km /h (15
m ph ). Th e ABM will t r y t o t est t h e pu m p m ot or. If
t h e br a ke peda l is a pplied t h e t est will be r u n a t 40
km /h (24 m ph ) r ega r dless of br a ke swit ch st a t e. If,
du r in g t h e dyn a m ic t est , t h e br a ke peda l is a pplied,
t h e dr iver m a y feel t h e t est t h r ou gh br a ke peda l
pu lsa t ion s. Th is is a n or m a l con dit ion .
If a n y com pon en t exh ibit s a t r ou ble con dit ion
du r in g syst em in it ia liza t ion or dyn a m ic ch eck, t h e
ABM will illu m in a t e t h e ABS wa r n in g in dica t or
a n d TCS In dica t or, if equ ipped.
3.3.6 ABS DIAGNOSTIC MODE
To en t er dia gn ost ic m ode, a veh icle speed m u st be
below 10 km /h (6 m ph ) a n d n o ABS con dit ion
pr esen t . If veh icle speed is n ot below 10 km /h
(6 m ph ), a "No Respon se" m essa ge cou ld be dis-
pla yed by t h e DRBIII . Th e followin g a r e ch a r a c-
t er ist ics of dia gn ost ic m ode:
– Th e a m ber ABS wa r n in g in dica t or will blin k
r a pidly. If a h a r d t r ou ble code, su ch a s Ba t t er y
Volt a ge Ou t of Ra n ge code is pr esen t , t h e
in dica t or will be illu m in a t ed wit h ou t blin kin g
u n t il t h e t r ou ble con dit ion is clea r ed.
– An t ilock oper a t ion is disa bled.
– Th e H CU va lves ca n n ot be a ct u a t ed wh en t h e
veh icle speed is a bove 8 km /h (5 m ph ). If va lve
a ct u a t ion is a t t em pt ed a bove 8 km /h (5 m ph ), a
"No Respon se" m essa ge will be displa yed on
t h e DRBIII .
3
Advertisement
Chapters
Table of Contents
Troubleshooting
