P0161 FORD O2 Sensor Heater Circuit Bank 2 Sensor 2

Possible causes
– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks
– Exhaust gas leaks
Tech notes
Replacing the Rear Heated Oxygen Sensor Bank 2 usually takes care of the problem.
When is the code detected?
Current amperage in the rear heated oxygen sensor heater circuit is out of the normal range.
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Possible higher than usual fuel consumption
P0161 FORD Description
The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.
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FORD Technical Service Bulletins for P0161 code
2001 FORD MUSTANG UNKNOWN OR OTHER
2001 FORD MUSTANG 980000 UNKNOWN OR OTHER
2001 FORD MUSTANG UNKNOWN OR OTHER
1999 FORD MUSTANG UNKNOWN OR OTHER
2000 FORD MUSTANG UNKNOWN OR OTHER
1999 FORD MUSTANG UNKNOWN OR OTHER
2000 FORD MUSTANG UNKNOWN OR OTHER
1999 FORD EXPLORER UNKNOWN OR OTHER
1999 FORD EXPLORER UNKNOWN OR OTHER