EC-518
[QG (WITHOUT EURO-OBD)]
DTC P0138 HO2S2
DTC P0138 HO2S2
PFP:226A0
Component DescriptionEBS00KGC
The  heated  oxygen  sensor  2,  after  three  way  catalyst  (manifold),
monitors the oxygen level in the exhaust gas.
Even  if switching  characteristics  of  the  heated  oxygen  sensor  1 are
shifted, the  air-fuel  ratio  is controlled to stoichiometric, by  the signal
from the heated oxygen sensor 2.
This sensor is made of ceramic zirconia. The zirconia generates volt-
age from approximately 1V in richer conditions to 0V in leaner condi-
tions.
Under normal conditions the heated oxygen sensor 2 is not used for
engine control operation.
CONSULT-II Reference Value in Data Monitor ModeEBS00KGD
Specification data are reference values.
On Board Diagnosis LogicEBS00KGE
The  heated  oxygen  sensor  2  has  a  much  longer  switching  time
between rich and lean than the heated oxygen sensor 1. The oxygen
storage capacity before the three way catalyst (manifold) causes the
longer  switching  time.  To  judge  the  malfunctions  of  heated  oxygen
sensor 2, ECM monitors whether the voltage is unusually high during
the various driving condition such as fuel-cut.
DTC Confirmation ProcedureEBS00KGF
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If “DTC Confirmation Procedure” has been previously conducted, always turn ignition switch “OFF” and wait at
least 10 seconds before conducting the next test.
SEF327R
MONITOR ITEM CONDITION SPECIFICATION
HO2S2 (B1)
●Engine: After warming up
●Keeping the engine speed 
between 3,500 and 4,000 rpm 
for one minute and at idle for 
one minute under no loadRevving engine from idle to 3,000 
rpm quickly.0 - 0.3V ←→ Approx. 0.6 - 1.0V
HO2S2 MNTR (B1)
●Engine: After warming up
●Keeping the engine speed 
between 3,500 and 4,000 rpm 
for one minute and at idle for 
one minute under no loadRevving engine from idle to 3,000 
rpm quickly.LEAN ←→ RICH
SEF301U
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0138
0138Heated oxygen sensor 2 
circuit high voltageAn excessively high voltage from the sensor 
is sent to ECM.
●Harness or connectors
(The sensor circuit is open or shorted.)
●Heated oxygen sensor 2