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Sensor Check
MPI SYSTEM
Check conditions
Test
Probable cause of malfunction
Check points
specification
(or action)
Self-diagnosis out-
o Engine: idling
Normal
o Check in accordance with the diag-
put
(2 minutes or'more after engine
nosis code.
start)
(Note that the diagnosis code will
be erased if there is disconnection
or damage of the engine control
unit back-up power-supply circuit.)
o If various diagnosis codes are out-
put, the most frequent
cause
is
damage or disconnection of the
power-supply or earth circuit.
Oxygen sensor
o Engine warm-up
Engine
Voltage (mV)
o If the oxygen sensor output voltage
o Service data
(Make the
condition
is high during sudden deceleration
o Item No.ll
mixture lean by
When sudden
250 or lower
1) Check for injector leakage.
engine speed
deceleration
2) Check the oxygen sensor signal
reduction, and
from 4,000
circuit.
rich by racing.)
rpm
o If the oxygen sensor output voltage
is low during engine racing
When engine
600-1,000
1) Check the oxygen sensor and
is suddenly
signal circuit.
raced
Engine: warm up
(using the oxygen
750 rpm
400 mV or
sensor signal,
(Idling)
lower
check the air/
(changes)
fuel mixture ratio,
and also check the
condition of control
2,000 rpm
by the engine
600-1,000 mV
control unit)
Air-flow sensor
o Engine warm-up
Engine
Frequency (Hz)
o If the air-flow sensor output fre-
o Service data
condition
quency suddenly changes greatly,
o Item No.12
improper contact of the air-flow
750 rpm
25-50
sensor or connector is probable.
(Idling)
o If the output frequency of the air-
2,000 rpm
70-130
-flow sensor is unusually high or
Racing
Increase
low, check the air cleaner element.
o If the output frequency of the air-
caused by
-flow sensor is high, an increase of
racing
engine resistance or leakage of
compression pressure is probable.
31-47
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