Mitsubishi 1989-1993 GALANT Service Manual page 230

FUEL SYSTEM
TROUBLESHOOTING HINTS
Hint I'
The exhaust gas purification performance will
worsen if there is a malfunction of the oxygen
sensor.
Hint 2:
If the oxygen sensor output voltage deviates from
the standard value even though the results of the
checking of the oxygen sensor are normal, the
cause is probably a malfunction of a component
related to mixture control.
INSPECTION
Using Scan tool
Data reading
HARNESS INSPECTION
FED
Harness
Harness side
Inspection conditions
Data display
Sensor de- Engine: warm up
(Make the mixture lean
tection vol-
by engine speed reduc-
tage
tion, and rich by racing)
Engine: warm up
(using the oxygen sen-
sor sianal. check the air/
fuel mixture ratio, and
also check the condition
of control by the engine
control module)
Check for an open-circuit, or a short-
Engine control
circuit to ground between the engine
module harness
side connector control module and the oxwen sen-
. r$;rdn sensor connector: Drscon-
. Engine control module connector:
Disconnected
Check for continuity of the ground
TSB Revision
Examples:
(2) Air leakage into the intake manifold from a
leaking gasket.
(3) Malfunction of the volume air flow sensor, the
intake air temperature sensor, the barometric-
pressure sensor, or the engine coolant tempera-
ture sensor.
Engine condition
When sudden decel-
eration from 4,000 rpm
When engine is sud-
750 rpm (Idling)
2,000 rpm
Standard value
lower
250 mV or
1,000 mV
400 mV or lower
(changes)
I I
,000 mV
Repair the
harness.
Ground)