Mitsubishi 1989 Galant, Service Manual

Page: 432 / 1273

FUEL SYSTEM <DOHC>
On-Vehicle Inspection of Components
HEATED OXYGEN SENSOR
to 1990.5 model-Non-Turbo, Turbo>
sensor connector
Theoretical
.-
5
14 15
16
Component side
Heated oxygen
. sensor
II
fuel
injection relay
II
Engine control module
Harness side
connector
OPERATION
l
The heated oxygen sensor functions to detect
the concentration of oxygen in the exhaust gas;
it converts those data to voltage, and inputs the
resulting signals to the engine control module.
l
If the air/fuel mixture ratio is richer than the
theoretical air/fuel mixture ratio (i.e., if the con-
centration of oxygen in the exhaust gas is
sparse), a voltage of approximately IV is output;
if the air/fuel mixture ratio in leaner than the
theoretical air/fuel mixture ratio (i.e., if the con-
centration is dense), a voltage of approximately
ov is output.
TROUBLESHOOTING HINTS
HINT 1:
The exhaust gas purification performance will wor-
sen if there is a malfunction of the heated oxygen
sensor.
Hint 2:
If the heated oxygen sensor output voltage deviates
from the standard value even though the results of
the checking of the heated oxygen sensor are nor-
mal, the cause is probably a malfunction of a com-
ponent related to mixture control.
l
The engine control module, based upon those
signals, regulates the amount of fuel injection so
that the air/fuel mixture ratio becomes the
theoretical air/fuel mixture ratio.
l
Battery power supply is applied, by way of the
fuel injection relay, to the oxygen sen-
sor heater. As a result, the sensor element is
heated by the heater, so that the heated oxygen
sensor shows excellent response even if the
temperature of the exhaust gas is low.
Examples:
(1) Malfunction of an injector.
(2) Air leakage into the intake manifold from a leak-
ing gasket.
(3) Malfunction of the volume air flow sensor, the
intake air temperature sensor, the
pressure sensor, or the engine coolant tempera-
ture sensor.
TSB Revision