Jeep Cherokee 1999 Electronic Service Manual page 1235

14 - 44 FUEL SYSTEM
DI AGN OSI S AN D T EST I N G (Cont inue d)
(6) Gr ou n d pin /ca vit y A-12 dir ect ly a t P CM u sin g a
sm a ll pa per clip. Be ca r efu l n ot t o da m a ge wir in g
wit h pa per clip. If en gin e idle speed in cr ea ses, it ca n
be a ssu m ed t h a t P CM is fu n ct ion in g cor r ect ly. Repa ir
open cir cu it in cir cu it K78. If en gin e idle speed will
n ot in cr ea se a ft er a pplyin g a gr ou n d t o pin /ca vit y
A-12 (cir cu it K78) dir ect ly a t P CM, r epla ce P CM.
THROTTLE POSITION SENSOR (TPS)
To per for m a com plet e t est of t h e TP S (F ig. 37) a n d
it s cir cu it r y, r efer t o t h e DRB sca n t ool a n d a ppr opr i-
a 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 TP S on ly, r efer t o t h e followin g:
Th e TP S ca n be t est ed wit h a digit a l volt m et er.
Th e cen t er t er m in a l of t h e TP S is t h e ou t pu t t er m i-
n a l.
Wit h t h e ign it ion key in t h e ON posit ion , ch eck t h e
TP S ou t pu t volt a ge a t t h e cen t er t er m in a l wir e of t h e
con n ect or. Ch eck t h is a t idle (t h r ot t le pla t e closed)
a n d a t Wide Open Th r ot t le (WOT). At idle, TP S ou t -
pu t volt a ge sh ou ld be gr ea t er t h a n .26 volt s bu t less
t h a n .95 volt s. At wide open t h r ot t le, TP S ou t pu t
volt a ge m u st be less t h a n 4.49 volt s. Th e ou t pu t volt -
a ge sh ou ld in cr ea se gr a du a lly a s t h e t h r ot t le pla t e is
slowly open ed fr om idle t o WOT.
THROTTLE BODY MINIMUM AIR FLOW CHECK
PROCEDURE
Th e followin g t est pr ocedu r e h a s been developed t o
ch eck t h r ot t le body ca libr a t ion s for cor r ect idle con di-
t ion s. Th e pr ocedu r e sh ou ld be u sed t o dia gn ose t h e
t h r ot t le body for con dit ion s t h a t m a y ca u se idle pr ob-
lem s. Th is p ro c e d u re s h o u ld be u s e d o n ly a fte r
n o rm a l d ia g n o s tic p ro c e d u re s h a v e fa ile d to
p ro d u c e re s u lts th a t in d ic a te a th ro ttle bo d y
re la te d p ro ble m . B e s u re to c h e c k fo r p ro p e r
o p e ra tio n o f th e id le a ir c o n tro l m o to r be fo re
p e rfo rm in g th is te s t.
A specia l fixed or ifice t ool (n u m ber 6714) (F ig. 40)
m u st be u sed for t h e followin g t est . Th is t ool h a s a
fixed in t er n a l dia m et er of 0.185".
Fig. 40 6714 Fixed Orifice Tool
(1) St a r t t h e en gin e a n d br in g t o oper a t in g t em -
per a t u r e. Be su r e a ll a ccessor ies a r e off befor e per-
for m in g t h is t est .
(2) Sh u t off en gin e a n d r em ove a ir du ct a t t h r ot t le
body.
(3) 2.5L 4–Cy lin d e r En g in e : Nea r fr on t /t op of
va lve cover, discon n ect CCV t u be a t fixed or ifice fit -
t in g (F ig. 41). In ser t Specia l Tool 6714 in t o en d of
discon n ect ed CCV t u be (in ser t eit h er en d of t ool in t o
t u be). Let t ool a n d t u be h a n g discon n ect ed a t side of
en gin e.
(4) 4.0L 6–Cy lin d e r En g in e : Discon n ect CCV
t u be (F ig. 42) a t in t a ke m a n ifold fit t in g. At t a ch a
sh or t piece of r u bber h ose t o specia l t ool 6714 (in ser t
r u bber h ose t o eit h er en d of t ool). In st a ll r u bber h ose/
t ool t o in t a ke m a n ifold fit t in g. Let CCV t u be h a n g
discon n ect ed a t side of en gin e.
Fig. 41 Install Orifice Tool 2.5L 4–Cylinder Engine
(5) Con n ect DRB sca n t ool t o 16–wa y da t a lin k
con n ect or. Th is con n ect or is loca t ed a t lower edge of
in st r u m en t pa n el n ea r st eer in g colu m n . Refer t o
a ppr opr ia t e P ower t r a in Dia gn ost ic P r ocedu r es ser-
vice m a n u a l for DRB oper a t ion .
(6) St a r t en gin e a n d a llow t o wa r m u p.
(7) Usin g t h e DRB sca n t ool, scr oll t h r ou gh m en u s
a s follows: select —St a n d Alon e DRB III, select 1999
Dia gn ost ics, select —E n gin e,
select —Min im u m Air F low.
(8) Th e DRB sca n t ool will cou n t down t o st a bilize
idle r pm a n d displa y m in im u m a ir flow idle r pm . Th e
idle r pm sh ou ld be bet ween 500 a n d 900 rp m . If idle
speed is ou t side t h ese specifica t ion s, r epla ce t h r ot t le
body. Refer t o Th r ot t le Body Rem ova l/In st a lla t ion .
(9) Discon n ect DRB sca n t ool fr om veh icle.
X J
select —Syst em Test ,