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SEF327R
Component Description
NFEC0904
The heated oxygen sensor 2, after three way catalyst, monitors the
oxygen level in the exhaust gas on each bank.
Even if switching characteristics of the heated oxygen sensor 1 are
shifted, the air fuel ratio is controlled to stoichiometric, by the sig-
nal from the heated oxygen sensor 2.
This sensor is made of ceramic zirconia. The zirconia generates
voltage from approximately 1V in richer conditions to 0V in leaner
conditions.
Under normal conditions the heated oxygen sensor 2 is not used
for engine control operation.
CONSULT-II Reference Value in Data Monitor
Mode
NFEC0905
Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
HO2S2 (B1)
HO2S2 (B2)
I Engine: After warming up
Revving engine from idle up to
2,000 rpm
0 - 0.3V +, Approx. 0.6 - 1.0V
HO2S2 MNTR
(B1)
HO2S2 MNTR
(B2)
LEAN +, RICH
SEF302U
On Board Diagnosis Logic
NFEC0907
The heated oxygen sensor 2 has a much longer switching time
between rich and lean than the heated oxygen sensor 1. The oxy-
gen storage capacity before the three way catalyst causes the
longer switching time. To judge the malfunctions of heated oxygen
sensor 2, ECM monitors whether the switching response of the
sensor’s voltage is faster than specified during the various driving
condition such as fuel-cut.
DTC No.
Trouble diagnosis
name
DTC Detecting Condition Possible Cause
P0139
0139
(Bank 1)
P0159
0159
(Bank 2)
Heated oxygen sen-
sor 2 circuit slow
response
It takes more time for the sensor to respond
between rich and lean than the specified time.
I Harness or connectors
(The sensor circuit is open or
shorted.)
I Heated oxygen sensor 2
I Fuel pressure
I Injectors
I Intake air leaks
GI
MA
EM
LC
FE
CL
MT
AT
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0139, P0159 HO2S2
Component Description
EC-257
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