Assuming the engine is a 4.3L, bank 1 would be on the drivers side.
behind the cat
Bank one sensor two refers to the oxygen sensor. The bank one sensor two oxygen sensor is on the front side of the engine, after the catalytic converter.
The oxygen sensor's are heated. so I guess that's where you are comming up with the word heated. Bank means- what side of the engine that the oxygen sensor is on. Bank 1 or bank 2
The P0155 refers to the Oxygen sensor on Bank 2, sensor 1. Bank 2 on your vehicle is on the passenger side of the engine. Sensor 1 is the first oxygen sensor in the exhaust pipe coming from the engine.
There is a failure in the oxygen sensor heater.
Bank # 1 is the passenger side of the engine Bank # 1 , SENSOR # 1 , is close to the engine in the exhaust Bank # 1 , SENSOR # 2 , is in the exhaust after the catalytic converter ( downstream )
Bank 1 oxygen sensor is the closest to the engine exhaust manifold. It is usually can seen and replaced if necessary with open hood.
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
In a Ford Expedition : Bank 1 is the passenger side of the engine Sensor 1 would be close to the engine before the exhaust enters the catalytic converter ( upstream sensor )
Bank 1 is the passenger side of the engine
The Bank 2 Sensor 2 oxygen sensor is typically located on the exhaust system, specifically after the catalytic converter on the side of the engine that corresponds to the second bank of cylinders. In a V-type engine, Bank 2 usually refers to the side opposite the bank containing cylinder number one. This sensor monitors the oxygen levels in the exhaust gases after they have passed through the catalytic converter, helping to optimize engine performance and emissions control.
Bank one is the side of the engine with cylinder #1. Sensor 2 is after the catalytic converter.