I am here today thinking that my father's O2 sensor on his 2003 Dodge Ram 2500 v8 van is bad, but I'm not 100% sure. Considering how expensive they are, I would like to have some other minds on this so that I may be more confident than I am right if/when I buy it.

The engine is misfiring, and the o2B1S2 was stuck on .9V on idle before I changed the spark plugs and spark plug wires. Now, it is stuck on exactly 1.000V. Does this mean that it is definitely stuck and needs replacing? ALSO: air filter is new and cylinders 1 and 2 (on both sides of the engine are misfiring)

  • What's the year and mileage?
    – tlhIngan
    Jun 7, 2017 at 4:24
  • What was the condition of the spark plugs? Did they show signs of carbon fouling or if another fault what was it?
    – GdD
    Jun 7, 2017 at 12:39
  • spark plugs did show carbon fouling and the year is 2003. I will edit this post again once I get the mileage. Jun 7, 2017 at 13:15

4 Answers 4


B1S2 oxygen sensor is the downstream sensor, i.e. after the catalyzer. It's responsible to perform diagnosis, not lambda control (mixture). Furthermore, being stucked is not a sign of a bad component.

B1S1 would be responsible for mixture. If you are able to measure it cycling than lambda control is definitely not your problem.


In my experience, bad O2 sensors don't cause misfires, they only cause poor gas-mileage and poor emissions. Here's a way to check:

The output of O2 sensors is only considered by the ECU once the engine has reached operating temperature. For the several minutes it takes to get the engine warmed up, the ECU is using "assumed values" instead of using the actual O2 sensor output. If the engine misfires during the warm-up phase, it is NOT the O2 sensor causing it.

Get to the source of your misfire. Check:

  • air filter, air duct going from the airbox to the throttle body for cracks, clean your mass airflow sensor (if you have one)
  • fuel filter (change it if it's older than 2 years), electrically test your fuel injectors, get your fuel lines cleaned
  • inspect your spark plugs, make sure they are gapped properly for that engine, use a timing light to make sure all plugs are firing
  • do a compression test on all cylinders, make sure they are pretty even

If you have an OBD scanner connect it and do NOT filter for just the O2 sensors, look at all of the results, if you find the malfunction great. I have found many issues with my ODB II meter that I probably would have guessed at and would have been wrong, if I was diagnosing without the ODBII.


Well, if you have already checked the electrical parts such as wires, coil,.. it could be the O2 sensor, since 0.9 and 1.0 are both high, and indicating a rich mixture. The normal value for a balanced mixture is about 0.45v.

And since you didn't mention any fluctuation in voltage, I believe it is a faulty circuit, maybe it is the regulator and not the sensor itself.

A good O2 sensor must show flip/flap voltage cause the ecu change the mixture that way to find a the good ratio each time you start.(however I am not too sure the dodge has this mechanism too, you have to check).

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