O2 Sensor Shorted to Ground

NAME OF CODE
02S Voltage Shorted To Ground

WHEN MONITORED
With engine coolant temperature above 170° F on the previous key on, after a cold start, engine coolant below 99° F, and ambient battery sensor reading within 27° F of engine coolant.

SET CONDITION
The oxygen sensor signal voltage is below 0.156 volts for 28 seconds after starting engine.

THEORY OF OPERATION
The oxygen sensor is a voltage generating device. The Powertrain Control Module (PCM) receives exhaust gas information from this 02 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 02 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 low, approximately 0.1 volt.

POSSIBLE CAUSES
- Sensor output wire shorted to ground
- Dirty/wet connection causing voltage tracking in connector
- 02 sensor failure
- Powertrain control module failure
- Connector terminals
- Connector wires