Jeep Cherokee 1999 Electronic Service Manual page 1232

X J
DI AGN OSI S AN D T EST I N G (Cont inue d)
Fig. 33 Rubber L-Shaped Fitting—MAP Sensor-to-
Throttle Body
ign it ion swit ch ON a n d en gin e OF F, ou t pu t volt a ge
sh ou ld be 4-t o-5 volt s. Th e volt a ge sh ou ld dr op t o 1.5-
t o-2.1 volt s wit h a h ot , n eu t r a l idle speed con dit ion .
Fig. 34 MAP Sensor Connector Terminals—Typical
(3) Test P ower t r a in Con t r ol Modu le (P CM) ca vit y
A-27 for sa m e volt a ge descr ibed a bove t o ver ify wir e
h a r n ess con dit ion . Repa ir a s n ecessa r y.
(4) Test MAP sen sor su pply volt a ge a t sen sor con -
n ect or bet ween t er m in a ls A a n d C (F ig. 34) wit h ign i-
t ion ON. Th e volt a ge sh ou ld be a ppr oxim a t ely 5 volt s
( 0.5V). F ive volt s ( 0.5V) sh ou ld a lso be a t ca vit y
A-17 of t h e P CM wir e h a r n ess con n ect or. Repa ir or
r epla ce wir e h a r n ess a s n ecessa r y.
(5) Test t h e MAP sen sor gr ou n d cir cu it a t sen sor
con n ect or t er m in a l—A (F ig. 34) a n d P CM con n ect or
A-4. Repa ir wir e h a r n ess if n ecessa r y.
Refer t o Gr ou p 8W, Wir in g Dia gr a m s for ca vit y
loca t ion s.
OXYGEN (O2S) SENSORS
To per for m a com plet e t est of t h e O2S sen sor s a n d
t h eir cir cu it r y, r efer t o t h e DRB sca n t ool a n d a ppr o-
pr ia t e P ower t r a in Dia gn ost ics P r ocedu r es m a n u a l. To
t est t h e O2S sen sor s on ly, r efer t o t h e followin g:
Th e u pst r ea m O2S sen sor is loca t ed on t h e exh a u st
down pipe (F ig. 35).
Th e down st r ea m O2S sen sor is loca t ed n ea r t h e
ou t let en d of t h e ca t a lyt ic con ver t er (F ig. 35).
Fig. 35 Oxygen Sensor Location
E a ch O2S h ea t in g elem en t ca n be t est ed wit h a n
oh m m et er a s follows:
Discon n ect t h e O2S sen sor con n ect or. Con n ect t h e
oh m m et er t est lea ds a cr oss t h e wh it e wir e t er m in a ls
of t h e sen sor con n ect or.
bet ween 4.5 .5 oh m s a n d 7 oh m s. Repla ce t h e sen -
sor if t h e oh m m et er displa ys a n in fin it y (open ) r ea d-
in g.
ENGINE COOLANT TEMPERA TURE SENSOR
To per for m a com plet e t est of t h e en gin e coola n t
t em per a t u r e sen sor a n d it s cir cu it r y, r efer t o DRB
sca n t ool a n d a ppr opr ia t e P ower t r a in Dia gn ost ics
P r ocedu r es m a n u a l. To t est t h e sen sor on ly, r efer t o
t h e followin g:
(1) Discon n ect wir e h a r n ess con n ect or fr om coola n t
t em per a t u r e sen sor (F ig. 36).
(2) Test t h e r esist a n ce of sen sor wit h a h igh in pu t
im peda n ce (digit a l) volt -oh m m et er. Refer t o SE NSOR
RE SISTANCE (OH MS)—COOLANT
TURE SE NSOR/INTAKE
SE NSOR ch a r t . Th e r esist a n ce (a s m ea su r ed a cr oss
sen sor t er m in a ls) sh ou ld be wit h in r a n ge sh own in
ch a r t . If n ot , r epla ce sen sor.
(3) Test con t in u it y of t h e wir e h a r n ess bet ween t h e
P CM wir e h a r n ess con n ect or a n d t h e coola n t sen sor
con n ect or t er m in a ls. Refer t o Gr ou p 8, Wir in g for t er-
m in a l/ca vit y loca t ion s. Repa ir t h e wir e h a r n ess if a n
open cir cu it is in dica t ed.
FUEL SYSTEM 14 - 41
Resist a n ce sh ou ld
TE MP E RA-
AIR TE MP E RATURE
be