M/T

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






General Description

The secondary heated oxygen sensor (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 secondary HO2S controls the air/fuel ratio with the A/F sensor output voltage to optimize TWC efficiency. When the secondary HO2S does not change during lean A/F when the throttle is closed, after full current is applied to the secondary HO2S heater, and output remains within the specified range continuously, a malfunction is detected.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold

The secondary HO2S output voltage is 0.05 V or more for at least 10 seconds.

Driving Pattern






1. Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T neutral) until the radiator fan comes on.
2. Drive the vehicle at a steady speed between 55 - 75 mph (88 - 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.

Diagnosis Details

Conditions for illuminating the MIL
When a malfunction is detected during the first drive cycle, a Temporary DTC is stored in the ECM/PCM memory. If the malfunction recurs during the next (second) drive cycle, the MIL comes on and the DTC and the freeze frame data are stored.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the diagnostic runs.The MIL, the DTC, the Temporary DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.