P0140 1/2 O2 Sensor StaysAt Center
NAME OF CODEO2 Sensor Stays at Center
WHEN MONITORED
With the engine running for more than 2 minutes and engine temperature greater than 170°.
SET CONDITION
The oxygen sensor signal voltage is between 0.35 volt and 0.55 volt for 1.5 minutes.
THEORY OF OPERATION
The oxygen sensor is a voltage generating device. The PCM receives exhaust gas information from this O2 sensor. The sensor detects exhaust gas content by a galvanic reaction within the sensor that produces a voltage. After measuring the amount of oxygen in the exhaust gases, the oxygen sensor tells the PCM how well its output signals are controlling the air/fuel ratio. Variations in the signal from this O2 sensor serve as air/fuel ratio indicators. Changes in the sensor signal occur because the air/fuel ratio is constantly changing. When oxygen content is low (rich mixture), the voltage signal will be approximately 1 volt. When oxygen content is high (lean mixture), the voltage signal will be low, approximately 0.1 volt.
POSSIBLE CAUSES
- Sensor output wire open
- O2 sensor failure
- Powertrain control module failure
- Dirt/moisture/grease causing voltage tracing in connector
- Connector wires