General Information

P0140 O2 Sensor Circuit No Activity Detected (Bank 1 / Sensor 2)

General Information

Component Location





General Description

The normal operating temperature of the HO2S (Heated Oxygen Sensor) ranges from 350 to 850 °C (662 to 1562 °F). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The PCM provides a pulse width modulated control circuit to adjust current through the heater. When the HO2S is cold, the value of the resistance is low and the current in the circuit is high. On the contrary, if the temperature in the resistor of the sensor rises, the current drops gradually.

DTC Description

Due to possible oxygen sensor defects (e.g. reference air poisoning) or faults in the injection system (e.g. leaking fuel injector), the rear oxygen sensor may not provide the expected lean or rich signal level during fuel cut-off or full load condition. Hence, the oxygen sensor signal is checked for plausibility during this engine operating states. There are 2 cases which DTC P0140 sets.
(I) Signal monitoring during fuel cut-off: The PCM monitors rear O2 sensor signal level during fuel cut-off which normally shows near 0 V and sets DTC P0140 when signal level is too high.
(II) Signal monitoring after fuel cut-off: The PCM monitors rear O2 sensor signal level after leaving fuel cut-off and sets DTC P0140 when signal remains at or below 0.6 V.

DTC Detecting Condition





Diagnostic Circuit Diagram





Signal Waveform & Data








Fig.1) HO2S signal waveform with idle after warm up :
1: Normal status (Approx. above 0.7 V), 2: Open in signal circuit (Approx. 0.4 - 0.5 V)