I have a 91 Honda Accord ex with about 217,000 miles on it. About 6 months ago my CEL came on, ran the code and it was a 43. So according to all my research and mechanics I know, code 43 is usually a bad o2 sensor.

So I replaced it. Only sensor I could get was a Bosch. So when the code came on again about 2-3 months later I wasn't too shocked considering all the bad things I've heard about Bosch. So I replaced it again, this time with a Denso.

Now it's been between 1-2 months and my CEL just comes on today. Of course it's code 43 again. So at this point I can't imagine it's the O2 sensor. What else could this be? Catalytic converter possibly?

 

A code 43 is tricky, because the description is vague. I had one one my 95 accord that would randomly pop up for years and couldn't figure out the problem.

I think the code pops up because the ECU can't get the air/fuel ratio correct. I don't think it is possible to read live data for the 91 accord to look at the fuel trims.

I'd start by looking for vacuum leaks.

Was there any work done on this car right before the problem popped up?

 

Besides air intake leaks, fuel delivery can also cause code 43. Suggest checking fuel pressure and looking for possible leaks at injector/fuel rail orings.

good luck

 

And don't forget about exhaust leaks. If the manifold is leaking, either at the head or the pipe, this can also "throw off" the O2 sensor readings causing the cade to set.

 

No there was not any repairs done before this code went off the first time. I'm only a basic repair man all of those things seem a little over my head. Would a basic repair man be able to make these diagnosis or would I be better off taking it to a mechanic? Which I like to put off as long as I can

 

Most mechanics seem to want to replace parts to see what works, since you pay for their mistakes. You need to find a good mechanic who will diagnose first, and call you to authorize repairs.

good luck