Jeep Cherokee 1999 Electronic Service Manual page 1220

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DESCRI PT I ON AN D OPERAT I ON (Cont inue d)
CAMSHAFT POSITION SENSOR—PCM INPUT
A syn c sign a l is pr ovide by t h e ca m sh a ft posit ion
sen sor loca t ed in t h e dist r ibu t or (F ig. 3). Th e syn c
sign a l fr om t h is sen sor wor ks in con ju n ct ion wit h t h e
cr a n ksh a ft posit ion sen sor t o pr ovide t h e P ower t r a in
Con t r ol Modu le (P CM) wit h in pu t s. Th is is don e t o
est a blish a n d m a in t a in cor r ect in ject or fir in g or der.
Refer t o Ca m sh a ft P osit ion Sen sor in Gr ou p 8D,
Ign it ion Syst em for m or e in for m a t ion .
Fig. 3 Camshaft Position Sensor—Typical
CRANKSHAFT POSITION SENSOR—PCM
INPUT
Th is sen sor is a h a ll effect device t h a t det ect s
n ot ch es in t h e flywh eel (m a n u a l t r a n sm ission ) or
flexpla t e (a u t om a t ic t r a n sm ission ).
Th is sen sor is u sed t o in dica t e t o t h e power t r a in
con t r ol m odu le (P CM) t h a t a spa r k a n d or fu el in jec-
t ion even t is t o be r equ ir ed. Th e ou t pu t fr om t h is
sen sor, in con ju n ct ion wit h t h e ca m sh a ft posit ion sen -
sor sign a l, is u sed t o differ en t ia t e bet ween fu el in jec-
t ion a n d spa r k even t s.
Th e sen sor is bolt ed t o t h e t r a n sm ission bellh ou s-
in g (F ig. 4).
Refer t o Gr ou p 8D, Ign it ion Syst em for m or e
cr a n ksh a ft posit ion sen sor in for m a t ion .
Th e en gin e will n ot oper a t e if t h e P CM does n ot
r eceive a cr a n ksh a ft posit ion sen sor in pu t .
ENGINE COOLANT TEMPERA TURE SENSOR—
PCM INPUT
Th e en gin e coola n t t em per a t u r e sen sor is in st a lled
in t h e t h er m ost a t h ou sin g (F ig. 5) a n d pr ot r u des in t o
t h e wa t er ja cket . Th e sen sor pr ovides a n in pu t volt -
a ge t o t h e P ower t r a in Con t r ol Modu le (P CM) r ela t in g
coola n t t em per a t u r e. Th e P CM u ses t h is in pu t a lon g
wit h in pu t s fr om ot h er sen sor s t o det er m in e in ject or
pu lse widt h a n d ign it ion t im in g. As coola n t t em per a -
t u r e va r ies, t h e coola n t t em per a t u r e sen sor 's r esis-
Fig. 4 Crankshaft Position Sensor—Typical
t a n ce ch a n ges. Th e ch a n ge in r esist a n ce r esu lt s in a
differ en t in pu t volt a ge t o t h e P CM.
Wh en t h e en gin e is cold, t h e P CM will oper a t e in
Open Loop cycle. It will dem a n d sligh t ly r ich er a ir-
fu el m ixt u r es a n d h igh er idle speeds. Th is is don e
u n t il n or m a l oper a t in g t em per a t u r es a r e r ea ch ed.
Refer t o Open Loop/Closed Loop Modes of Oper a -
t ion in t h is sect ion of t h e gr ou p for m or e in for m a t ion .
Fig. 5 Engine Coolant Temperature Sensor—Typical
FUEL SYSTEM 14 - 29