Downstream O2 Sensor Heater Failure

Name of Code:
Downstream O2 Sensor Heater Failure

When Monitored:
With the ignition key oft, after the engine cools down

Set Condition:
No sensor output signal is received when the PCM powers up the sensor heater.

Theory of Operation:
The downstream 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 downstream oxygen sensor tells the PCM how well the catalytic converter is oxidizing HC and CO components and reducing NOx components in the engine exhaust gas. This O2 sensor serves as an indicator of oxygen content. The heater element helps the O2 sensor quickly reach a normal and steady operating temperature, which is required for proper emission control.

Possible Causes:
- Open heater element circuit
- O2 sensor failure
- Powertrain control module failure
- Connector terminals
- Connector wires