Question about 2003 Mercury Grand Marquis
Need to raise the car and get under it.
Bank 2 would be the passenger side, and sensor 1 would be the pre-catalyst sensor (closer to the engine).
The O2 sensors read te amount of oxygen before and after the Catalyst (catalytic converter). The Cat is between the engine and the muffler. The sensors are on both sides of the Cat in the exhaust pipe. there is a special socket that makes removal easy. Most are 7/8 or 22mm.
Use some thread sealer on the new one.
Pretty easy job.
Posted on Feb 02, 2010
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Posted on Jan 02, 2017
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Fig. Fig. 3: Oxygen sensor-4.3L engines
Fig. Fig. 4: Oxygen sensor-5.0L and 5.7L engines
Fig. Fig. 5: Oxygen sensor-7.4L engines
Oxygen sensors are always numbered like this:
Bank 1 sensor 1
Bank 2 sensor 1
Bank 1 sensor 2
Bank 2 sensor 2
Some manufacturers use a kind of shorthand that reads different, but means the same thing:
Sensor 1/1 or O2s 1/1
Sensor 2/1 or O2s 2/1
Sensor 1/2 or O2s 1/2
Sensor 2/2 or O2s 2/2
Bank 1 is always the side of the engine where cylinder number 1 is located and, of coarse, Bank 2 is the opposite side.
On a 4 cylinder engine, there is only 1 bank and it is always referred to as Bank 1.
Sensor 1 is always the upstream sensor (the one located BEFORE the catalytic converter)
Sensor 2 is always the downstream sensor (the one that is located AFTER the catalytic converter.
Hope helps (remember to rate this).
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