3l, 6 cyl (California emissions). Where is the 4th O2 or (A/F) sensor?
I can find 3 of the 4 O2 or (A/F)(O2)sensors. Standing in front of car, I see the 1st one coming out of manifold in the 1st cat.on the right side of engine. Under the car > still towards the front of the engine I see 2 more O2 sensors. Where is The 4th one?
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Re: 3l, 6 cyl (California emissions). Where is the 4th...
HO2S( heated sensor) are before the cat convertor either in the manifold or exhaust pipe to the cat converter
O2 sensors are in the exhaust after the cat converter/s
I am drawing the difference because they are not all O2 sensors as each has a different operation for the position in the exhaust
the missing one will be in the exhaust manifold or pipe at a convenient position for servicing before the cat converter
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You did not say what your car was ,however most newer cars use 2 oxygen sensors per bank, if it is a 4 cyl replace downstream o2 sensor,if 6 or 8 cyl bank 1 sensor 2 is downstream sensor on bank that has cyl 1 on it.upstream sensor is in front of catalytic converter downstream is after the cat
Look under the hood for the emission class sticker.
Smog check station's machine in CA are programmed to handle both types.
You do not need to change anything before the inspection.
You should check the service record for the last Catalytic converter,O2 sensors and EGR valve change.
Service interval for
Catalytic ~180,000 miles
O2 ~150,000 miles
EGR ~160,000 miles
If you can locate the last smog test (even from out of state)
Check for the
6 cyl. and 8 cyl. engines are divided into 2 Banks, standing in front of the Engine, the Bank 1 is the side where the #1 spark plug is (on V6 Ford Engines is on the PASSENGER SIDE). Bank 2 is on the DRIVERS SIDE.
Check the following diagram for HO2 sensor locations (This diagram applies to Ranger, Explorer and Mountaineer models) :
2 would be Bank 1 and 2A would be Bank 2.
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Standing in front of the car looking at the engine bank 1 is the cylinders on the front of the engine. These are cylinders 1-3-5. On the rear is bank 2 cylinders 2-4-6. The O2 sensor is located screwed into the exhaust manifold or the exhaust pipe on the front of the engine.
Well, if you have the 6 cylinder, there are 3 02 sensors in that car.
One on front manifold, one on back manifold, and one in the center pipe.You changed one, good idea to change the other 2. That is if you have the 6 cyl.