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8A - 2
BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
A l l vehicles are equipped w i t h O B D (except diesel).
A l l O B D sensing systems are monitored b y the Sin-
gle Board E n g i n e Controller. The Engine Controller
w i l l store i n electronic memory any detectable f a i l u r e
w i t h i n the monitored circuits. Refer t o U S I N G O N -
B O A R D D I A G N O S T I C S Y S T E M i n t h i s group for
more i n f o r m a t i o n .
CHECK ENGINE
LAMP
ALTERNATOR
BATTERY
J908A-15
Fig. 2 Charging System Components (Typical)
B A T T E R Y T E S T P R O C E D U R E S ON V E H I C L E
INDEX
Page
Battery Load Test
. 5
Causes of Battery Discharging
3
Charging Battery
6
General Information
2
Page
Ignition Off Draw (IOD)
4
Open Circuit Voltage Test
4
State of Charge Test
3
Test Indicator
. 3
GENERAL INFORMATION
The battery stores, stabilizes, and produces electri-
cal current t o operate various electrical systems i n
the vehicle. T h e d e t e r m i n a t i o n of whether a b a t t e r y
is good or bad is made b y the batteries a b i l i t y t o ac-
cept a charge a n d produce high-amperage c u r r e n t
o u t p u t over a n extended period. The capability o f the
battery to store electrical current comes f r o m a
chemical reaction between the sulfuric acid solution
(electrolyte) and the lead + /-plates i n each cell o f the
battery. As the battery discharges, t h e plates collect
the acid from t h e electrolyte. When the c h a r g i n g sys-
t e m charges t h e battery, the acid is forced out o f the
plates into the electrolyte. The amount o f acid (spe-
cific gravity) i n the electrolyte can be measured w i t h
a hydrometer. A factory installed battery is equipped
w i t h a b u i l t - i n hydrometer (test indicator) t o assist
i n d e t e r m i n i n g t h e batteries state-of-charge. The fac-
t o r y i n s t a l l e d b a t t e r y is also nonrefillable, water can-
not be added. The battery i s vented t o release gases
t h a t a r e created w h e n the b a t t e r y is being charged.
The b a t t e r y t o p , posts, a n d t e r m i n a l s should be
cleaned w h e n other underhood maintenance is per-
formed (Fig. 3).
WARNING: DO NOT ATTEMPT TO ASSIST BOOST,
CHARGE, OR TEST BATTERY WHEN ELECTRO-
LYTE LEVEL IS BELOW THE TOP OF THE PLATES
(YELLOW OR BRIGHT COLOR DOT IS VISIBLE).
PERSONAL INJURY MAY OCCUR.
W h e n t h e electrolyte level is below the top of t h e
plates (yellow or b r i g h t color indicator ttot), the bat-
t e r y m u s t be replaced. T h e b a t t e r y m u s t be com-
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