DTC Advanced Diagnostics: P0139
DTC P0139:Secondary Heated Oxygen Sensor (Secondary HO2S (Sensor 2)) Slow Response

General Description


The secondary heated oxygen sensor (secondary HO2S (sensor 2)) detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) during stoichiometric air/fuel ratio feedback control. The powertrain control module (PCM) controls the air/fuel ratio with the air/fuel ratio (A/F) sensor (sensor 1) output voltage to optimize the TWC's efficiency. When the secondary HO2S (sensor 2) does not change during lean air/fuel ratio when the throttle is closed, after full current is applied to the secondary HO2S (sensor 2) heater, and output remains within the specified range continuously, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle
Sequence
P0138 is judged as OK
Duration
10 seconds or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Elapsed time after starting the engine
2 minutes
–
Engine coolant temperature
[ECT SENSOR 1]
156 °F (69 °C)
–
Intake air temperature
[IAT Sensor (1)]
-13 °F (-25 °C)
–
Engine speed
[ENGINE SPEED]
–
4,000 rpm
Secondary HO2S output voltage [HO2S S2]
0.05 V
–
Intake air amount
2 g/second (0.07 oz/second)
–
Fuel feedback
During deceleration
[ ]: HDS Parameter

Malfunction Threshold
The secondary HO2S (sensor 2) output voltage [HO2S S2] is 0.05 V or more for at least 10 seconds.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
Secondary HO2S (sensor 2) responsive deterioration
Exhaust system failure (exhaust gas leak)

Confirmation Procedure
Operating Condition

1.
Start the engine. Hold the engine speed [ENGINE SPEED] at 3,000 rpm without load (CVT in P or N, M/T in neutral) until the radiator fan comes on, then let it idle for at least 2 minute.
2.
Drive the vehicle at a steady speed between 55 - 75 mph (89 - 120 km/h) for at least 1 minute.
3.
Decelerate with the throttle valve fully closed for at least 10 seconds.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
With the HDS
None.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.