MPI <4G6> -
Troubleshooting
13A-37
Code No. P0420 Catalyst malfunction Probable cause
Range of Check
D
The engine speed is 3,000 r/min or less.
D
During driving
D
During air/fuel ratio feedback control
Set Conditions
D
The ratio between the oxygen sensor (rear) and the oxygen sensor (front)
output frequencies reaches 0.8 per 12 seconds on average.
D
Malfunction of catalyst
D
Malfunction of the oxygen sensor (front)
D
Malfunction of the oxygen sensor (rear)
D
Malfunction of engine-ECU <M/T>
D
Malfunction
of
engine-A/T
-ECU
<A/T>
NG
Replace
the
engine-ECU
<M/T>
or
engine-A/T
-ECU
<A/T>.
Check the trouble symptoms.
NG
Replace the catalytic converter.
Check the trouble symptoms.
OK
Replace the oxygen sensor (rear).
Replace the oxygen sensor (front).
NG
OK
MUT-
II
Data list
11 Oxygen sensor (front)
D
Transmission:
2nd
gear
<M/T>,
L
range
<A/T>
OK:
Changeover between 0 - 400 mV and 600 - 1,000
mV occur 15 times in 10 seconds.
NG
Check the oxygen sensor (front) system <sensor 1>
(Refer to P.13A-21, INSPECTION PROCEDURE FOR
DIAGNOSTIC TROUBLE CODE P0130.)
MUT-
II
Data list
11 Oxygen sensor (front)
OK:
600 - 1,000 mV when racing suddenly
OK
NG
Check the oxygen sensor (rear) system <sensor 2>
(Refer to P.13A-24, INSPECTION PROCEDURE FOR
DIAGNOSTIC TROUBLE CODE P0136.)
OK
MUT-
II
Data list
59 Oxygen sensor (rear)
D
Transmission:
2nd
gear
<M/T>,
L
range
<A/T>
D
Drive with wide open throttle
OK:
600 - 1,000 mV
Check the exhaust manifold. (Are there any cracks?)
NG
Repair
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