Jeep Cherokee 1999 Electronic Service Manual page 367

8F - 6 AUDIO SYSTEMS
DI AGN OSI S AN D T EST I N G (Cont inue d)
NOTE: This model has a two-piece antenna coaxial
cable. Tests 2 and 4 must be conducted in two
steps to isolate a coaxial cable problem; from the
coaxial cable connection under the right end of the
instrument panel near the right cowl side inner
panel to the antenna base, and then from the coax-
ial cable connection to the radio chassis connec-
tion.
Fig. 1 Antenna Tests
TEST 1
Test 1 det er m in es if t h e a n t en n a m a st is in su la t ed
fr om t h e ba se. P r oceed a s follows:
(1) Un plu g t h e a n t en n a coa xia l ca ble con n ect or
fr om t h e r a dio ch a ssis a n d isola t e.
(2) Con n ect on e oh m m et er t est lea d t o t h e t ip of
t h e a n t en n a m a st . Con n ect t h e ot h er t est lea d t o t h e
a n t en n a ba se. Ch eck for con t in u it y.
(3) Th er e sh ou ld be n o con t in u it y. If con t in u it y is
fou n d, r epla ce t h e fa u lt y or da m a ged a n t en n a ba se
a n d ca ble a ssem bly.
TEST 2
Test 2 ch ecks t h e a n t en n a for a n open cir cu it a s
follows:
(1) Un plu g t h e a n t en n a coa xia l ca ble con n ect or
fr om t h e r a dio ch a ssis.
(2) Con n ect on e oh m m et er t est lea d t o t h e t ip of
t h e a n t en n a m a st . Con n ect t h e ot h er t est lea d t o t h e
cen t er pin of t h e a n t en n a coa xia l ca ble con n ect or.
(3) Con t in u it y sh ou ld exist (t h e oh m m et er sh ou ld
on ly r egist er a fr a ct ion of a n oh m ). H igh or in fin it e
r esist a n ce in dica t es da m a ge t o t h e ba se a n d ca ble
a ssem bly. Repla ce t h e fa u lt y ba se a n d ca ble, if
r equ ir ed.
TEST 3
Test 3 ch ecks t h e con dit ion of t h e veh icle body
gr ou n d con n ect ion . Th is t est sh ou ld be per for m ed
wit h t h e ba t t er y posit ive ca ble r em oved fr om t h e ba t -
t er y. Discon n ect bot h ba t t er y ca bles, t h e n ega t ive
ca ble fir st . Recon n ect t h e ba t t er y n ega t ive ca ble a n d
per for m t h e t est a s follows:
(1) Con n ect on e oh m m et er t est lea d t o t h e veh icle
fen der. Con n ect t h e ot h er t est lea d t o t h e ba t t er y
n ega t ive post .
(2) Th e r esist a n ce sh ou ld be less t h a n on e oh m .
(3) If t h e r esist a n ce is m or e t h a n on e oh m , ch eck
t h e br a ided gr ou n d st r a p con n ect ed t o t h e en gin e a n d
t h e veh icle body for bein g loose, cor r oded, or da m -
a ged. Repa ir t h e gr ou n d st r a p con n ect ion , if r equ ir ed.
TEST 4
Test 4 ch ecks t h e con dit ion of t h e gr ou n d bet ween
t h e a n t en n a ba se a n d t h e veh icle body a s follows:
(1) Con n ect on e oh m m et er t est lea d t o t h e veh icle
fen der. Con n ect t h e ot h er t est lea d t o t h e ou t er cr im p
on t h e a n t en n a coa xia l ca ble con n ect or.
(2) Th e r esist a n ce sh ou ld be less t h en on e oh m .
(3) If t h e r esist a n ce is m or e t h en on e oh m , clea n
a n d/or t igh t en t h e a n t en n a ba se t o fen der m ou n t in g
h a r dwa r e.
RADIO FREQUENCY INTERFERENCE
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL,
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
F or com plet e cir cu it dia gr a m s, see Gr ou p 8W -
Wir in g Dia gr a m s. In spect t h e gr ou n d pa t h s a n d con -
n ect ion s a t t h e followin g loca t ion s:
• Blower m ot or
• E lect r ic fu el pu m p
• E n gin e-t o-body gr ou n d st r a p
• Gen er a t or
• Ign it ion m odu le
• Ra dio a n t en n a ba se gr ou n d
• Ra dio r eceiver ch a ssis gr ou n d wir e or st r a p
• Wiper m ot or.
If t h e sou r ce of RF I or E MI n oise is iden t ified a s a
com pon en t on t h e veh icle (i.e., gen er a t or, blower
m ot or, et c.), t h e gr ou n d pa t h for t h a t com pon en t
sh ou ld be ch ecked. If excessive r esist a n ce is fou n d in
a n y gr ou n d cir cu it , clea n , t igh t en , or r epa ir t h e
GROUP 8M - PASSIVE
STEERING COLUMN,
X J
OR