second O2 sensor??????

[andys2]

I have a JDM ej20G out of some sort of Legacy. This is the engine with a black AWIC. Anyway, I'm in the process of puitting it into my impreza and I can't figure out about this second O2 sensor.

One of the 02 sensors is a three wire unit - this is the one I have connected. The other is a 2 wire unit - and I have no idea where it connects to. I have been using the wiring schematics from a 92 Liberty RS and a 94 WRX - neither of which have two O2 sensors. \

Concidently I also have two unknown wires on the ECU (a16 & d9). I don't think these are for the O2 sensor as the wiring doesn't match. Any ideas?

BTW I have been very careful with the wiring and am pretty comfortable with the info from the doccumentation. So far the major difference between the Liberty-RS and the WRX info is the way the fans and AC control are organized. Neither of which I care about very much.

Finally, I also don't have much info on how the whole select reading / read data / read memory interface works. Anyone have any info onm this?

thanks,

-Andy

[Legacy777]

what year did the JDM engine come out of?

[andys2]

I have no idea of the model year. Does it make that much of a difference?

[gnuman]

I have no idea of the model year. Does it make that much of a difference?

Yes, as the model years you mentioned only use one O2 sensor for fuel trim. the second one (which really should be a 4 wire unit) is to monitor the efficiency of the cat (to get a finer tuning of the fuel mix, and to determine if the cat dies). If the engine is from a recent model year (post 1996 I think), then it will have the second cat on it, otherwise not.

[andys2]

yes, but the first O2 sensor goes to the ECU - the second O2 sensor, the two wire one, doesn't go to the ecu. It goes somewhere else. Where could it have gone?

uh oh - looks like some road blocks

[gnuman]

It should go to the ECU. . .