how do you know which oxygen sensor is bad on 96 neon , it came up a code 21?

Answer 1

You retrieved the codes according to the OLD protocol for Chrysler, (as opposed to the OBD II code reader)and it is accurate as far as it goes.
"21" indicates something wrong with the CIRCUIT for the sensor, which could be something like a loose connection, broken wire, or corrosion somewhere. When you go under the car, check ALL possibilities, then replace the sensor.
The car(s) before only had the forward sensor for each bank, and a 4-cylinder only has one bank. Change the one in the exhaust manifold or exhaust pipe. The sensor behind the Catalytic converter cannot generate a code that can be retrieved by cycling the key.

A professional note------> Replace both of them, as the PCM wants to "see" reaction and response of both, and while replacing one of them MAY correct the code issue, it won't help much in the way of emissions control or fuel economy.

Good Luck

Answer 2

first ur car is not a 96 ill bet its a 95 in 1996 the fed gov said obd II must be installed on all cars and the code we read either p1 or p0xxx so if its 21 u probablyonly have one oxy sensor and its a single wire sensor if u have two one before the catalytic conver and one after, just replace both save ur self the time from when the other goes out

Answer 3

If it's a 96 than it should of had a P--- code. Better check your car or your scanner or what your doing.

Answer 4

Hook your car with OBD II inspection.It will tell you exactly which one is bad,like bank 1,or bank 2.

Answer 5

go to the local autozone have them read the codes and they will be able to tell you if it is front or rear