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X J
DESCRI PT I ON AN D OPERAT I ON (Cont inue d)
• E GR va lve con t r ol solen oid (if equ ipped)
• E VAP ca n ist er pu r ge solen oid
• F ive volt sen sor su pply (pr im a r y)
• F ive volt sen sor su pply (secon da r y)
• F u el in ject or s
• F u el pu m p r ela y
• Gen er a t or field dr iver (-)
• Gen er a t or field dr iver (+)
• Idle a ir con t r ol (IAC) m ot or
• Ign it ion coil
• Lea k det ect ion pu m p (if equ ipped)
• Ma lfu n ct ion in dica t or la m p (Ch eck en gin e la m p).
Dr iven t h r ou gh CCD cir cu it s.
• Ra dia t or coolin g fa n r ela y
• Speed con t r ol va cu u m solen oid
• Speed con t r ol ven t solen oid
• Ta ch om et er (if equ ipped). Dr iven t h r ou gh CCD
cir cu it s.
• Tr a n sm ission con ver t or clu t ch cir cu it
MODES OF OPERA TION
As in pu t sign a ls t o t h e power t r a in con t r ol m odu le
(P CM) ch a n ge, t h e P CM a dju st s it s r espon se t o t h e
ou t pu t devices. F or exa m ple, t h e P CM m u st ca lcu la t e
differ en t in ject or pu lse widt h a n d ign it ion t im in g for
idle t h a n it does for wide open t h r ot t le (WOT).
Th e P CM will oper a t e in t wo differ en t m odes:
Op e n Lo o p a n d Clo s e d Lo o p .
Du r in g Open Loop m odes, t h e power t r a in con t r ol
m odu le (P CM) r eceives in pu t sign a ls a n d r espon ds
on ly a ccor din g t o pr eset P CM pr ogr a m m in g. In pu t
fr om t h e oxygen (O2S) sen sor s is n ot m on it or ed du r-
in g Open Loop m odes.
Du r in g Closed Loop m odes, t h e P CM will m on it or
t h e oxygen (O2S) sen sor s in pu t . Th is in pu t in dica t es
t o t h e P CM wh et h er or n ot t h e ca lcu la t ed in ject or
pu lse widt h r esu lt s in t h e idea l a ir-fu el r a t io. Th is
r a t io is 14.7 pa r t s a ir-t o-1 pa r t fu el. By m on it or in g
t h e exh a u st oxygen con t en t t h r ou gh t h e O2S sen sor,
t h e P CM ca n fin e t u n e t h e in ject or pu lse widt h . Th is
is don e t o a ch ieve opt im u m fu el econ om y com bin ed
wit h low em ission en gin e per for m a n ce.
Th e fu el in ject ion syst em h a s t h e followin g m odes
of oper a t ion :
• Ign it ion swit ch ON
• E n gin e st a r t -u p (cr a n k)
• E n gin e wa r m -u p
• Idle
• Cr u ise
• Acceler a t ion
• Deceler a t ion
• Wide open t h r ot t le (WOT)
• Ign it ion swit ch OF F
Th e ign it ion swit ch On , en gin e st a r t -u p (cr a n k),
en gin e wa r m -u p, a cceler a t ion , deceler a t ion a n d wide
open t h r ot t le m odes a r e Open Loop m odes. Th e idle
a n d cr u ise m odes, (wit h t h e en gin e a t oper a t in g t em -
per a t u r e) a r e Closed Loop m odes.
IGNITION SWITCH (KEY-ON) MODE
Th is is a n Open Loop m ode. Wh en t h e fu el syst em
is a ct iva t ed by t h e ign it ion swit ch , t h e followin g
a ct ion s occu r :
• Th e power t r a in con t r ol m odu le (P CM) pr e-posi-
t ion s t h e idle a ir con t r ol (IAC) m ot or.
• Th e P CM det er m in es a t m osph er ic a ir pr essu r e
fr om t h e MAP sen sor in pu t t o det er m in e ba sic fu el
st r a t egy.
• Th e P CM m on it or s t h e en gin e coola n t t em per a -
t u r e sen sor in pu t . Th e P CM m odifies fu el st r a t egy
ba sed on t h is in pu t .
• In t a ke m a n ifold a ir t em per a t u r e sen sor in pu t is
m on it or ed.
• Th r ot t le posit ion sen sor (TP S) is m on it or ed.
• Th e a u t o sh u t down (ASD) r ela y is en er gized by
t h e P CM for a ppr oxim a t ely t h r ee secon ds.
• Th e fu el pu m p is en er gized t h r ou gh t h e fu el
pu m p r ela y by t h e P CM. Th e fu el pu m p will oper a t e
for a ppr oxim a t ely t h r ee secon ds u n less t h e en gin e is
oper a t in g or t h e st a r t er m ot or is en ga ged.
• Th e O2S sen sor h ea t er elem en t is en er gized via
t h e ASD r ela y. Th e O2S sen sor in pu t is n ot u sed by
t h e P CM t o ca libr a t e a ir-fu el r a t io du r in g t h is m ode
of oper a t ion .
ENGINE START-UP MODE
Th is is a n Open Loop m ode. Th e followin g a ct ion s
occu r wh en t h e st a r t er m ot or is en ga ged.
Th e power t r a in con t r ol m odu le (P CM) r eceives
in pu t s fr om :
• Ba t t er y volt a ge
• E n gin e coola n t t em per a t u r e sen sor
• Cr a n ksh a ft posit ion sen sor
• In t a ke m a n ifold a ir t em per a t u r e sen sor
• Ma n ifold a bsolu t e pr essu r e (MAP ) sen sor
• Th r ot t le posit ion sen sor (TP S)
• Ca m sh a ft posit ion sen sor sign a l
Th e P CM m on it or s t h e cr a n ksh a ft posit ion sen sor.
If t h e P CM does n ot r eceive a cr a n ksh a ft posit ion
sen sor sign a l wit h in 3 secon ds of cr a n kin g t h e
en gin e, it will sh u t down t h e fu el in ject ion syst em .
Th e fu el pu m p is a ct iva t ed by t h e P CM t h r ou gh
t h e fu el pu m p r ela y.
Volt a ge is a pplied t o t h e fu el in ject or s wit h t h e
ASD r ela y via t h e P CM. Th e P CM will t h en con t r ol
t h e in ject ion sequ en ce a n d in ject or pu lse widt h by
t u r n in g t h e gr ou n d cir cu it t o ea ch in dividu a l in ject or
on a n d off.
Th e P CM det er m in es t h e pr oper ign it ion t im in g
a ccor din g t o in pu t r eceived fr om t h e cr a n ksh a ft posi-
t ion sen sor.
FUEL SYSTEM
14 - 25
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