Hi, new here I have a 97 civic LX and recently threw a primary o2 sensor error code, upon investigation I found the dreaded cracked exhaust manifold these models are known for. I replaced it with an aftermarket assembly that fit great but had seperate cat and exhaust manifold with a gasket and bolts in between, not like the ex conversion but not one piece anymore. I got all new gaskets and mounting bolts and got it to fit to the best of my DIY ability and p fairly confident I don't have any leaks from it not fitting perfectly and for good measure I replaced both upstream and downstream sensors I found on amazon that had good reviews from users using in my same model engine. The exhaust and cat replacement was reviewed good as well. All was well and fired up and ran great for about the first 40 miles then the CEL came back with the same code, I re set and it ran great for 20 miles then came back again. What steps should I take next before just seeing if I got a bad sensor or cutting losses and saying I got the wrong cat/exhaust kit? Thanks for any help advice or info.

 

Which code exactly? Check for leaks carefully by having someone block the tailpipe while you listen under the hood for any exhaust leaking out. Cat performance doesn't affect the first sensor since it is before the cat. Do you still have the original sensor to try it?

 

I am pretty sure it was p1035 for the heated main o2 sensor circuit failure. My old manifold was cracked end to end with the primary sensor in the middle and burnt to ****, it failed a multimeter test so plugging the old one back in is a no go. I'll try and check for exhaust leaks. I've read elsewhere certain censors while technically within specs for your car can still give you issues being slightly off from OEM. Also worried my replacement assembly was just different enough to perpetuate my problem. Although now I'm pulling no error code from my ecu log, but the CEL is on... what gives there?

 

Scatch that actually got my reader to pull p0135 heater sensor bank 1 fault code. Still it is a brand new evan fischer sensor. Possibly the wrong one? Or check my wiring? Have only done about 25 miles city driving I'd that enough for a new sensor and exhaust/cat system to adjust to my ecu? Thanks for any info or help again.

 

Heater code means the sensor is bad, or it is not getting power from the harness. Too much or too little oxygen is a different code. Since you have a 1997, the fuse 15 problem should be mentioned, though that results in several codes including heater codes for both sensors.

The sensor heater is the two wires on the sensor that are the same color (usually black). With the sensor cold, unplug it and there should be a closed circuit (I think 10-40 ohms) between the two heater wires. You should have 12 volts on one wire all the time with the key on. The ECU pulls the other wire to ground to heat up the sensor.

 

only use DENSO or NTK sensors in honda's anything else will give you problems. also these sensors are very fragile i would suggests buying from a local parts store not amazon.

 

I changed my fuse #15 and checked for exhaust leaks and all good there. Reset my CEL to see if it comes back again, after this I bought a multimeter to test my wiring and make sure it's supplying the right power to my primary sensor. If all the doesn't work I'm gonna replace my sensor with a Denso or Honda one and I'll update with my results to help anyone elaw in case they see this thread and share my issues. Thanks everyone for the advice!

 

If fuse 15 blew that means you need to check and tape up the wires behind the engine. They get frayed and short out intermittently, so it's going to blow again.

 

The fuse was good, I just changed for good measure or OCD whichever you want to call it. I'm gonna try an NGK or Denso sensor tomorrow and see if that's it from autozone as recommended before. Thanks. Will update for any one else's future reference