I pulled a code 21 from my 95 dodge neon. Code 21: Problem with oxygen sensor signal circuit. Sensor voltage to computer not fluctuating. What could be wrong with the o2 sensor? Also im going on a trip to PA about 300 miles will this give me problems?

 

could mean that one of the o2 sensors went bad or just sensed something wrong... my o2 sensor pass my Cat. went off when my cat. went bad...but then it went off...sometimes they are just picky... not sure if it would cause major problems or not but the first o2 sensor may change the fuel to air mixture so it might change your fuel mileage... but all depends...

 

If the o2 sensor is over 100,000 miles old its more than likely burnt out... Go ahead and replace both at the same time (not really nessesary till the other one dies but I would anyway)... You can still drive on a bad o2 sensor but your mpg will most likely suffer a little bit and since your taking a road trip you will want to squeeze out every mile you can get per gallon...

 

how much is a o2 sensor?

 

for my car from autozone... roughly 60 for the cheapest...