I owned 96 Honda, It misfire on my way home. I don’t know what's wrong with it .For I just change the battery and alternator, so I read the fault code with my fault reader and it shown P0328, P0340, P0420, P0031.What's the code? Is it easy if I repair myself?

 

the po328 is knock sensor circuit performance,this sensor plays a major role in the electric spark control.check it replace if needed.
po340 is no camshaft position sensor signal at powertrain control module,check connection at the sensor.you mite be able to test it not sure?replace if needed.
po420 upstream catalytic converter efficiency below threshold.mite be a clogged up converter?take it to the shop.
And p0031 is shorted condition in upstream O2 sensor heater control feedback sensing circuit.really no way to check 02 sensors?
But before you go out an buy all these sensors i would have your PCM (Powertrain Control Module) checked out 1st.Rarely do the PCM go bad but it does and has happened!so before you go spend a few hundred bucks on sensors spend a hundred and have the PCM checked.
goodluck!

 

I have moved this to the proper section.

 

When there are multiple codes, it may be due to a short somewhere and possibly one or more blown fuses. Check fuses first and then try to locate the source of the possible short. -- It may even be related to the alternator wiring since you mentioned the battery and alternator was just replaced.

 

thanks guys.

 

Good post with good answers...Great Guys!

 

sounds like the components replaced were due to a no charge condition with a wiped out battery...this can cause all kinds of havoc on the computer system/sensors...clear the codes and see which ones come back, if any. they all can be checked/diagnosed, including the oxygen sensors.