I have a 1992 Civic VX. The check engine light was on when I bought it. The previous owner said he replaced the oxygen sensor, but he didn't know what else to do. After buying it, I started trying to diagnose it. I have a code 9 and 48. One relates to the lean fuel sensor, the other to the cam sensor. The car seems to run fine, but when I cleared the check engine light, it immediately came back on. My diagnostic tests point to a possible bad ECU, because it doesn't seem to be communicating. The oxygen sensor and the distributor check out good. According to the sticker under the hood, my car is a California emissions car. The part number on the ECU confirms this.
I posted my question on Honda-Tech.com. I was told that California emissions cars came with a 4-wire O2 sensor instead of a 5-wire, and that the Cali. cars had no EGR.
Well, my car has a 5-wire sensor and an EGR.
So now I'm confused. I know there are some VX experts (vxperts?) in here. Can anyone help me figure this out?
OK, I've received some info from others. Apparently in 1992 only ALL VXs came with a 5-wire sensor. The difference between Cali. and Fed. emissions was only the programming in the ECU. Cali. emissions had the lean burn disabled. Starting in 1993 Honda put a 4-wire sensor on Cali. cars.
So now my question is: If I replace my Cali. ECU with a Fed. ECU will the car now have lean burn?
Yes, you will have lean burn if all you switch is the ECU. That's what I did and the increase in mileage was worth it. I was scared something was going to fry because I couldn't find anyone that did it before, but everything has been fine.
However, get ready to feel a slight hesitation at times when the engine is getting out of lean burn. Not a big deal, but thought I should mention it. In my opinion I don't think the codes you are getting are related to the ECU.