Jeep Cherokee 1999 Electronic Service Manual page 1215

14 - 24 FUEL SYSTEM
OXYGEN SENSOR . . . . . . . . . . . . . . . . . . . . . . . 48
POWER STEERING PRESSURE SWITCH—2.5L
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
POWERTRAIN CONTROL MODULE (PCM) . . . . 47
THROTTLE BODY . . . . . . . . . . . . . . . . . . . . . . . 45
THROTTLE POSITION SENSOR (TPS) . . . . . . . 46
DESCRI PT I ON AN D OPERAT I ON
POWERTRAIN CONTROL MODULE (PCM)
Th e P ower t r a in Con t r ol Modu le (P CM) (F ig. 1)
oper a t es t h e fu el syst em . Th e P CM wa s for m er ly
r efer r ed t o a s t h e SBE C or en gin e con t r oller. Th e
P CM is a pr e-pr ogr a m m ed, t r iple m icr opr ocessor dig-
it a l com pu t er. It r egu la t es ign it ion t im in g, a ir-fu el
r a t io, em ission con t r ol devices, ch a r gin g syst em , cer-
t a in t r a n sm ission fea t u r es, speed con t r ol, a ir con di-
t ion in g com pr essor clu t ch
speed. Th e P CM ca n a da pt it s pr ogr a m m in g t o m eet
ch a n gin g oper a t in g con dit ion s.
Fig. 1 PCM Location
Th e P CM r eceives in pu t sign a ls fr om va r iou s
swit ch es a n d sen sor s. Ba sed on t h ese in pu t s, t h e
P CM r egu la t es va r iou s en gin e a n d veh icle oper a t ion s
t h r ou gh differ en t syst em com pon en t s. Th ese com po-
n en t s a r e r efer r ed t o a s P ower t r a in Con t r ol Modu le
(P CM) Ou t pu t s. Th e sen sor s a n d swit ch es t h a t pr o-
vide in pu t s t o t h e P CM a r e con sider ed P ower t r a in
Con t r ol Modu le (P CM) In pu t s.
Th e P CM a dju st s ign it ion t im in g ba sed u pon
in pu t s it r eceives fr om sen sor s t h a t r ea ct t o: en gin e
r pm , m a n ifold a bsolu t e pr essu r e, en gin e coola n t t em -
per a t u r e, t h r ot t le posit ion , t r a n sm ission gea r selec-
t ion (a u t om a t ic t r a n sm ission ), veh icle speed, power
st eer in g pu m p pr essu r e (2.5L en gin e on ly), a n d t h e
br a ke swit ch .
Th e P CM a dju st s idle speed ba sed on in pu t s it
r eceives fr om sen sor s t h a t r ea ct t o: t h r ot t le posit ion ,
veh icle speed, t r a n sm ission gea r select ion , en gin e
en ga gem en t a n d idle
VEHICLE SPEED SENSOR . . . . . . . . . . . . . . . . 50
SPECIFICATIONS
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . 51
SPECIAL TOOLS
FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . 52
coola n t t em per a t u r e a n d fr om in pu t s it r eceives fr om
t h e a ir con dit ion in g clu t ch swit ch a n d br a ke swit ch .
Ba sed on in pu t s t h a t it r eceives, t h e P CM a dju st s
ign it ion coil dwell. Th e P CM a lso a dju st s t h e gen er-
a t or ch a r ge r a t e t h r ou gh con t r ol of t h e gen er a t or
field a n d pr ovides speed con t r ol oper a t ion .
NOTE: PCM Inputs:
• A/C r equ est (if equ ipped wit h fa ct or y A/C)
• A/C select (if equ ipped wit h fa ct or y A/C)
• Au t o sh u t down (ASD) sen se
• Ba t t er y t em per a t u r e
• Ba t t er y volt a ge
• Br a ke swit ch
• CCD bu s (+) cir cu it s
• CCD bu s (-) cir cu it s
• Ca m sh a ft posit ion sen sor sign a l
• Cr a n ksh a ft posit ion sen sor
• Da t a lin k con n ect ion for DRB sca n t ool
• E n gin e coola n t t em per a t u r e sen sor
• E xt en ded idle swit ch (4.0L en gin e wit h police
pa cka ge)
• F u el level
• Gen er a t or (ba t t er y volt a ge) ou t pu t
• Ign it ion cir cu it sen se (ign it ion swit ch in on /off/
cr a n k/r u n posit ion )
• In t a ke m a n ifold a ir t em per a t u r e sen sor
• Lea k det ect ion pu m p (swit ch ) sen se (if equ ipped)
• Ma n ifold a bsolu t e pr essu r e (MAP ) sen sor
• Oil pr essu r e
• Oxygen sen sor s
• P a r k/n eu t r a l swit ch (a u t o. t r a n s. on ly)
• P ower gr ou n d
• P ower st eer in g pr essu r e swit ch (2.5L en gin e
on ly)
• Sen sor r et u r n
• Sign a l gr ou n d
• Speed con t r ol m u lt iplexed sin gle wir e in pu t
• Th r ot t le posit ion sen sor
• Veh icle speed sen sor
NOTE: PCM Outputs:
• A/C clu t ch r ela y
• Au t o sh u t down (ASD) r ela y
• CCD bu s (+/-) cir cu it s for : speedom et er, volt m e-
t er, fu el ga u ge, oil pr essu r e ga u ge/la m p, en gin e t em p.
ga u ge a n d speed con t r ol wa r n . la m p
• Da t a lin k con n ect ion for DRB sca n t ool
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