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SEF484Y
On Board Diagnosis Logic
NHEC0214
The ECM monitors the switching frequency ratio of heated oxygen
sensors 1 (front) and 2 (rear).
A three way catalyst (Manifold) with high oxygen storage capacity
will indicate a low switching frequency of heated oxygen sensor 2
(rear). As oxygen storage capacity decreases, the heated oxygen
sensor 2 (rear) switching frequency will increase.
When the frequency ratio of heated oxygen sensor 1 (front) and 2
(rear) approaches a specified limit value, the three way catalyst
(Manifold) malfunction is diagnosed.
Malfunction is detected when three way catalyst (Manifold) does
not operate properly, three way catalyst does not have enough
oxygen storage capacity.
Possible Cause
NHEC0504
I Three way catalyst (Manifold)
I Exhaust tube
I Intake air leaks
I Injectors
I Injector leaks
I Spark plug
I Improper ignition timing
GI
MA
EM
LC
FE
AT
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0420 (BANK 1), P0430 (BANK 2) THREE WAY CATALYST FUNCTION
On Board Diagnosis Logic
EC-357
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