car type: 98 civic ex 2 door coupe
what have you guys replaced to get rid of this error code?

 

that means your catalytic converter is not working, or your secondary oxygen sensor is not working

 

have you had this error if so what did you replace?

 

I haven't had that code on my Civic. But if I did, I would replace either the catalytic converter, or the secondary oxygen sensor

 

To figure out if your cat is bad or if your O2 sensor is bad you will need a scan tool (or a scope). Hook up the scan tool and look at the secondary O2 sensor voltages (and the primary at the same time if you can). If the secondary O2 sensor waveform looks like a sine/cosine function, then your cat is not working properly. Also, you can disconnect a vacuum line or spray carb cleaner into the throttle. Look at the secondary and primary sensor waveforms. If they are still the same, then most likely the cat is no good. If your O2 sensor is no good, you will see a really weird waveform (not anything like a sine or cosine) or the waveform will be stuck at one voltage. A working cat and secondary O2 sensor will show a straightish line around 0v (I think its 0). If you have a scope but not a scan tool, I can also help you hook it up to do the same test.

 

i have a tektronix oscilloscope, where do i hook up the scope probe?

 

Hook up the scope to the signal wires for the 2 O2 sensors. One O2 on channel 1 and the other on channel 2. I'm pretty sure that you can use a common ground so hook up the ground to somewhere on the body. I've never actually done it with a scope before, I've used the scan tool in the past. This method should also work but I'm not 100% positive since I've never tried it.

 

Should be the white wire on the sensors. The full-scale signal is about +0.8 volts. If you see it varying smoothly then the sensor is good but the cat is bad. If it sits at zero or jumps around randomly the sensor needs to be replaced.

 

ok -i'll try it
thanks for your help

 

one thing i found strange is that i reset the car and the engine light has not come on in 5 days. if the sensor was bad i think the engine light would come on instantly after reseting. just a thought