Possible causes

– Downstream O2 sensor harness is open or shorted
– Downstream O2 sensor circuit poor electrical connection
– Exhaust leak near O2 sensor
– Faulty O2 sensor
– Fuel contamination

When is the code detected?

The Engine Control Module (ECM) has detected a fault with the downstream O2 sensor

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)