OBD-II Trouble Code Description for P0166 Ford

O2 Sensor Circuit No Activity Detected

What does this mean?

OBD2 Code P0166 Ford definition:
The rear heated oxygen sensor (or sensor 3 for some vehicles), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of the heated oxygen sensor 1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the signal from the heated oxygen sensor 3. This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. Under normal conditions the heated oxygen sensor 3 is not used for engine control operation.

Symptoms

Possible sumptoms of OBD code P0166 Ford
– Engine Light ON (or Service Engine Soon Warning Light) – High Fuel Consumption – Excessive Smoke from Exhaust

Causes

Possible causes of OBD code P0166 Ford
– Harness or connectors (The sensor circuit is open or shorted) – Rear heated oxygen sensor (Bank 2) may be faulty The Error code is generally activated on detection of the following conditions: Current amperage in the rear heated oxygen sensor heater circuit is out of the normal range. (An improper voltage drop signal is sent to ECM through the rear heated oxygen sensor heater