Anyone know if the p28 reads the four wire or the five wire o2 sensor when plugged into a 98 civic? I still can't figure out why it won't just plug and play.

Confused

 

4-wire

 

well I can't figure this out then. I know that my five wire is bad because as soon as I put a header on I threw a bad o2 bay 1 code. I purchased a p28 and wire harness and plugged it in the rpm @idle shot up to 2200-2500 up and down. I let it sit for a minute to see if it would learn but it didn't change. I have checked the vac lines and didn't find a leak. Don't know what's going on but have been driving with an engine light for a while now.

 

If my p28 is socketed but has no chip will this cause a problem?

 

You mean it's looking for an external ROM but you have no external ROM installed? That will put the ECU into backup, limp-home mode instantly, with a low rev limiter... something like 3.5k.

If that's the case, cut jumper J1 and return the ECU to stock.

 

You can NOT use a P28 with a 5-wire O2 sensor.

 

so how do I go about this? My hx is wired with a 5 wire and a four wire. I can't figure out which wire it reads because I can't find a replacement 5 wire to plug in to see stock ecu clears code with new 5 wire becasue the only five wire I can find costs $400. Do I need to re-wire or is there a way to by-pass and make the #2 4 wire port the main port.

 

You need to rewire the 5 wire O2 plug with a 4 wire plug.

I believe board members Dax (link in sig), dwnthehatch (link in sig), and VTECVillian are excellent sources for this information (as well as the search).