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SEF484Y
On Board Diagnosis Logic
NGEC1042
The ECM monitors the switching frequency ratio of heated oxygen
sensor 1 (front) and 2 (rear).
A three way catalyst* with high oxygen storage capacity will indi-
cate a low switching frequency of rear heated oxygen sensor. As
oxygen storage capacity decreases, the rear heated oxygen sen-
sor switching frequency will increase.
When the frequency ratio of front and rear heated oxygen sensors
approaches a specified limit value, the three way catalyst* malfunc-
tion is diagnosed.
*: Warm-up three way catalyst (For California)
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0420
0702
쐌 Three way catalyst does not operate properly.
쐌 Three way catalyst does not have enough oxygen stor-
age capacity.
쐌 Three way catalyst*
쐌 Exhaust tube
쐌 Intake air leaks
쐌 Injectors
쐌 Injector leaks
쐌 Spark plug
쐌 Improper ignition timing
*: Warm-up three way catalyst (For California)
SEF671Y
SEF672Y
DTC Confirmation Procedure
NGEC1043
NOTE:
If “DTC Confirmation Procedure” has been previously
conducted, always turn ignition switch “OFF” and wait at least
5 seconds before conducting the next test.
TESTING CONDITION:
쐌 Open engine hood before conducting following proce-
dure.
쐌 Do not hold engine speed more than specified minutes
below.
With CONSULT-II
1) Turn ignition switch “ON”.
2) Select “DTC & SRT CONFIRMATION” then “SRT WORK SUP-
PORT” mode with CONSULT-II.
3) Start engine.
4) Rev engine up to 2,500 to 3,500 rpm and hold it for 3 consecu-
tive minutes then release then accelerator pedal completely.
If “INCMP” of “CATALYST” changes to “CMPLT”, go to step 7.
5) Wait 5 seconds at idle.
6) Rev engine up to 2,000 to 3,000 rpm and hold it until “INCMP”
of “CATALYST” changes to “CMPLT”. (It will take maximum of
approximately 5 minute.)
SEF560X
7) Select “SELF-DIAG RESULTS” mode with CONSULT-II.
If the 1st trip DTC is detected, go to “DIAGNOSTIC
PROCEDURE”, EC-283. If not “COMPLT” stop engine and
cool down “COOLANT TEMP/SE” to less than 70°C (158°F)
and then retest from step 1).
DTC P0420 THREE WAY CATALYST FUNCTION
KA24DE
On Board Diagnosis Logic
EC-347
FE
CL
MT
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
GI
MA
EM
LC
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