Chrysler - Plymouth - Dodge Neon oxygen sensor replacement
Oxygen sensors are standard wear items that last about 60,000 to 100,000 miles depending on gasoline, engine conditions, and the like. You should probably get an oxygen sensor socket (it has a slot to let the wire through) before starting - about $10-$15. You will also need standard metric sockets from 10mm to 15mm and antiseize compound. When you do this, the exhaust manifold should be warm but not burn-hot. Running the car for one minute may well be enough.
The oxygen sensor generally runs about $38-$50. We paid $38 over the counter of a local parts store for a Standard "low line" which looked the same as the Standard "high line."
First, remove the coil pack (held on by three nuts) and the air intake hose (between the air filter and throttle body - it's big, black, and you can't miss it; loosen the hose clamps with a 9 mm socket). The reason for removing the coil pack is to provide room to get the airbox out, but you can probably finesse the airbox out if you really, really don't want to remove the coil pack (which is pretty easy to do.)
Now take off the air snorkle or intake horn; and remove the two nuts on hold the air filter box on (on some cars, they're on the back; on ours, one was on the bottom of the airbox, under the filter, and the other was outside; they needed a 10 mm socket). You can then remove the air filter box by lifting up firmly; when taking it out, be careful of the two mounting thingies that stick out of the bottom and can catch wires and houses. (For more detailed instructions, see above.)
The two oxygen sensors will now be very much out in the open - the upstream one is between the engine and the catalytic converter, and the downstream is on the other end of the catalytic converter. However, to make it easier to remove the upstream sensor, I took out the ledge that the airbox sits on. It is held in by two 13 mm bolts which came right out and provided better access to the upstream sensor.
Remove the wire from the oxygen sensor (you'll have to pull the connector up and out of its mount first), put antiseize compound (just a little) on the threads of the new sensor (unless it came that way), and tighten it to 30 lb-ft (snug but not too tight). Put everything back together. Remember to attach the connector back to the little hole.
Total time for my first time, knowing very little: 15 minutes.
Warning from Mark McMackin, Chrysler Group Senior Specialist: “[Don’t spray silicone or WD40 in the connector. Those two fluids will kill an O2 quicker than lighting. The sensor needs to breath oxygen (O2) and it does it through the wiring. Silicone will send a sensor’s output south so fast you won't know what hit you.”