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• M a n i f o l d Absolute Pressure ( M A P ) Sensor
• N e u t r a l Safety S w i t c h
• Oxygen Sensor
• T h r o t t l e Position Sensor
• T h r o t t l e Body Temperature Sensor (5.2L a n d 5.9L
engines)
• Vehicle Distance Sensor
S B E C O u t p u t s
• A/C C l u t c h Relay
• A i r S w i t c h i n g Solenoid
•
A l t e r n a t o r
• A u t o S h u t d o w n (ASD) Relay
• Canister Purge Solenoid
• Check E n g i n e L a m p
• Diagnostic Connector
• E G R Solenoid
• E M R L a m p
• F u e l Injectors
• Idle Speed C o n t r o l (ISC) Actuator
• I g n i t i o n C o i l
• Overdrive
a n d Lock-up Torque
Converter
Sole-
noids
• Shift I n d i c a t o r L a m p
The A u t o m a t i c S h u t D o w n (ASD) relay i s mounted
externally, b u t is switched o n and off b y t h e SBEC.
The relay provides voltage for t h e electric fuel pump,
fuel injector, i g n i t i o n coil a n d exhaust gas oxygen
sensor heater element. T h e SBEC monitors t h e dis-
t r i b u t o r pick-up s i g n a l t o determine engine speed
a n d compute injector synchronization. I f t h e SBEC
does n o t receive a d i s t r i b u t o r signal w h e n t h e i g n i -
t i o n switch i s i n t h e " R U N " position, i t w i l l n o t en-
ergize t h e A S D relay, stopping t h e b a t t e r y voltage
supply t o t h e fuel injector, fuel pump, i g n i t i o n coil,
a n d oxygen sensor heater element.
The SBEC contains a voltage converter w h i c h con-
verts b a t t e r y voltage to a regulated 8.0 volts t o
power t h e d i s t r i b u t o r pick-up. T h e SBEC also pro-
vides a five (5) v o l t supply for t h e M a n i f o l d Absolute
Pressure ( M A P ) sensor and T h r o t t l e Position Sensor
(TPS).
A/C SWITCH-SBEC INPUT
W h e n t h e A/C s w i t c h is i n t h e O N position, t h e
SBEC receives a n i n p u t i n d i c a t i n g t h a t t h e a i r con-
d i t i o n i n g h a s been selected. A f t e r receiving t h i s i n -
p u t the SBEC activates the A/C compressor clutch b y
g r o u n d i n g t h e A/C c l u t c h relay, and m a i n t a i n s idle
speed to a scheduled R P M t h r o u g h control o f the Idle
Speed C o n t r o l A c t u a t o r .
The SBEC w i l l de-energize t h e A/C clutch relay i f
i t receives i n p u t f r o m either t h e A/C l o w pressure
s w i t c h i n d i c a t i n g a l o w refrigerant level, o r from t h e
electric c l u t c h cycling s w i t c h i n g i n d i c a t i n g evapora-
t o r freezing.
BATTERY VOLTAGE—SBEC INPUT
The SBEC monitors t h e battery voltage i n p u t t o
determine fuel injector pulse w i d t h a n d a l t e r n a t o r
field control.
I f battery voltage is low the SBEC w i l l increase i n -
jector pulse w i d t h (period of t i m e t h a t t h e injector i s
energized)
t o compensate
for t h e reduced
flow
t h r o u g h t h e injector caused b y t h e lowered voltage.
BRAKE LIGHT SWITCH-SBEC INPUT
W h e n t h e brake l i g h t switch is activated, t h e
SBEC receives a n i n p u t i n d i c a t i n g t h a t t h e brakes
are being applied. After receiving
t h i s i n p u t t h e
SBEC m a i n t a i n s idle speed t o a scheduled R P M
t h r o u g h control o f the Idle Speed C o n t r o l A c t u a t o r .
COOLANT TEMPERATURE SENSOR-SBEC INPUT
The Coolant Temperature Sensor i s i n s t a l l e d n e x t
to the thermostat housing i n the i n t a k e m a n i f o l d w a -
ter jacket passage and provides a n i n p u t voltage t o
the SBEC (Fig. 3). A s coolant temperature varies t h e
Coolant Temperature Sensors resistance changes r e -
s u l t i n g i n a different i n p u t voltage t o t h e SBEC.
W h e n t h e engine is cold, t h e SBEC w i l l demand
s l i g h t l y richer air-fuel m i x t u r e s a n d h i g h e r
idle
speeds u n t i l
n o r m a l operating
temperatures are
reached.
Fig. 3 Coolant Temperature Sensor
ENGINE SPEED-SBEC INPUT
The engine speed i n p u t is supplied to t h e SBEC b y
the d i s t r i b u t o r pick-up. The d i s t r i b u t o r pick-up i s a
H a l l Effect device (Fig. 4).
A shutter (sometimes referred to as a n i n t e r r u p t e r )
is attached to t h e distributor shaft. T h e s h u t t e r con-
tains one blade per engine cylinder (six blades for
the 3.9L engine or eight blades for the 5.2L and 5.9L
engines). A switch plate is mounted to the d i s t r i b u t o r
housing above t h e shutter. The switch plate contains
the d i s t r i b u t o r pick-up (a H a l l Effect
device a n d
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