My 1997 Accord has 205,000 miles on it. The CEL light came on so I took it to Auto Zone. Their scanner gave no code so they said it was probably the oxygen sensor. Later I took it to Advance Auto. They said it gave a bad O2 sensor reading so I bought one.. Later realized it was a universal one. Took it to exchange for one with the right plug. Different guy checked it and said it was the downstream O2 sensor He seemed to think this was somewhat unusual. He said it was possible my cat converter was bad causing it to get too hot and causing it to throw a code. Car is running fine, getting 27 mpg same as always. My question is what do I do first. Since it's an old car I know the muffler shop will want to replace the cat. I can change the sensor myself, but if I do that and still get a code should I replace one or both sensors? By the way I replaced the muffler about a year ago. They didn't say anything about the cat, but I didn't ask them to check it. I tend to think it's the sensor since it first threw a code shortly (2-3 min.) after I started driving. Does the converter get that hot that fast?

 

Post the actual trouble code number.

 

Guy didn't give me the number. I'm going to check again at Auto Zone and see if they can get a code this time. Buddy of mine had his cel come on, couldn't get a code been driving it for 3 years.

 

My son had that issue with his Civic shortly after he installed LEDs in his dash. Kept coming on without throwing a code. He changed it back to a "normal" bulb and the light went out. Only thing we could figure out was there might not have been enough resistance for it (the LED) to keep it turned off.

OP, find out if it's an upstream or downstream O2 sensor. The upstream sensor controls the mix, while the downstream O2 sensor monitors the cat only. This is not saying either are bad, but just what each 1 does.

Tomorrow I've got to throw the scanner on and see what the code is on my 99 Accord. The light's been off ever since I changed out the exhaust system (cat included). I'll find out if I should have changed the O2 sensor while I was in there. If it's not the sensor, I have a feeling my dreaded code P1457 came back. We'll see.