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Re: Where are the upstream o2 senser on a 1996 olds 3.1
It should be ahead of The Cat. Converter or just below the Exhaust Manifold.....It looks like a Spark Plug with a 14 Ga. wire coming out of it with a connector that can be unplugged for removal.....Maybe 13/16th hex........
That is the first sensor closest to the engine. The downstream sensor is the one behind the converter.
Good luck. Please rate this response , and let me know if ya need more help!
If you have trouble codes stored in your cars computer for O2 sensors a fuse will not fix it. One or all of the O2's may need to be replaced. There are test that can be done to confirm which one.
There are 2 pre-cat o2's and 2 post cat o2's. Jack up the car and look, you will see them on the exhaust system. You can use a special wrench or just a opened wrench.The two after the car do nothing as far as emmisions are concerned, but will cause a check engine light. The two in front are used for engine control. The O2 sensors monitor the O2 level of the exhaust. If the O2 it too high, (lean) the ECU adds fuel. Conversly too little (rich)and it reduces fuel. Either way they are vital to keeping your engine running at its optimum.o replace your oxygen sensors you'll need
Jack (2 ton rating or higher)
Jack Stands (3 ton rating or higher)
Safety glasses -- protect your eyes from falling debris!
22mm 6/12 point crows foot oxygen sensor socket.
3/8" swivel head ratchet or breaker bar (handle no longer than 10 inches)
Oxygen sensors appropriate to the exact model and year vehicle.
sensor branding.
Fig. 2: Pre-Cat Sensor Plugs
Fig. 3: Pre-Cat Sensors on Headers
To replace the pre-catalyst sensors:
Jack up the front of the car and put the car securely on jack stands. If you support the car only by the jack, it's likely you won't live long enough to reap the benefits of your new sensors.
Crawl under the car from the front (with your head pointing at the rear of the vehicle) and look on the right side of the motor for the exhaust manifolds. On OBD I cars the single pre-cat oxygen sensor is located near the y-pipe joint, but on all OBD II cars they're located in the headers just aft of where the pipes of the three cylinders join into a single pipe.
Attempt to loosen each oxygen sensor. The reason we do this first is simple -- if you can't loosen them, there's no sense in continuing. If you manage to get both sensors loose, continue to the next step. If not, make sure the sensors are tight before you extract yourself from under the vehicle. Exhaust leaks are no fun.
Remove the fuel rail cover on the engine. This is the long and thin cover toward the driver's side of the engine. I also removed the larger cover for additional clearance at the rear of the engine but it's not essential you do so.
Take note of the oxygen sensor plugs on the top of the fuel rail cover. The sensor closest to the front of the car is for Bank 2 (cylinders 4, 5, 6, or the rear-most three cylinders) while the other is naturally for Bank 1 (cylinders 1, 2, 3). The pre-catalyst sensors will always be the same part number and thus be interchangeable. However, the leads must not be crossed between the banks or the engine will run roughly. For this reason I advocate replacement of one sensor at a time to ensure that everything goes back together properly. See Figure 2.
The oxygen sensor leads run from the plu gs to the back of the engine, then along the rear of the valve cover toward the passenger's side of the engine where they drop vertically along the side of the engine and eventually rearward to meet the respective sensors. Begin by removing the small black "c-clips" that retain the leads on the top of the engine. Set them aside outside of the engine bay for safe keeping.
Pick a sensor plug to remove. Follow the lead toward and along the back of the engine. It is held in place on the rear and side of the engine by bendable metal tabs. Carefully bend these tabs open so the lead(s) can be removed. There are a couple tabs on the rear of the engine near the valve cover that can be reached while standing in front of the car. The remainder of the tabs must be reached from under the vehicle. You may need to work some of the tabs loose by feel. See figure 3 and note in this picture that I've already loosened the tabs somewhat.
Once you've worked the lead loose, pull it down toward the sensor so you can loosen the sensor without the wires twisting. While you have new sensors available, the goal is to preserve the old sensors in case one of the new sensors is DOA.
Remove the sensor using the crows foot socket. I found that my 3/8" SK breaker bar and its pivoting head worked wonders on this job. You could use a ratchet with a pivoting head as well. For a peek at the condition of my original sensors with all of 140K miles on them,
Post-Catalyst SensorsReplacement of the post-cat sensors uses the same techniques as the pre-cat units but the post-cats require removal of the mid-section for access. The sensor plugs are located under the cover used to protect the fuel filter so you'll need to remove that. Thanks. keep updated for any more query.you can rate this solution
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find the plug unplug it use a O2 socket turn ounter clockwise to remove should be located in the exhaust manifold or infront of the cat teh one behind the cat is the downstreme
The answer depends on the type of exhaust system you have. You will have either 3 or 4 total O2 sensors on your V8. If you have single exhaust with a single catalytic converter then you will have 3 O2 sensors (2 upstream sensors & one downstream sensor - "up or down stream" meaning before of after the catalytic converter). If you have either dual exhaust and/or two catalytic converters then you have 4 O2 sensors (2 upstream & 2 downstream). If you have an MIL light (malfunction indicator light, or "check engine light") the code will indicate "front bank / bank one", which is one of the 2 upstream O2's before the catalytic converter(s), or "rear bank / bank two", which is one of the O2's after the catalytic converter(s).
did u change the right o2 sensor there is 2 sensors on bank1 and 2 on bank2.....upstream and down stream.....i had the same prob i changed the o2 senser to the other side to check and make sure it was the o2 senser....it took 4 o2 sensors before i got 1 that finally worked nd yes i was buying them brand new.....so change sides with it nd see if the code changes sides....and did u reset it with the code machine when u put the new 1 in?
depends on the engine setup. 4 cylinder single exhaust. one upstream o2 before converter. one downstream o2 after converter.
v configures engines will have two upstream. if it has two converters it will have two downstream. one converter only one downstream o2.
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