was showing P1193 and P1138, now showing P1191 and P1138...????
 

OK, so I was getting the following codes from my 98 D1:

P1138 Oxygen Sensor Engine Rich *Codes* A D
P0158 Oxygen Sensor High Voltage *Codes* B D
P1193 Oxygen Sensor Heater Circuit Open Downstream

So I figured the problem was post-xat O2 sensors. I bought 4 used O2 sensors, which the previous owner said weren't throwing any codes...

Replaced both post-cat O2 sensors and am now getting:

P1191 Oxygen Sensor Heater Circuit Open Downstream
P1138 Oxygen Sensor Engine Rich *Codes* A D

So the engine rich reading for Bank A is happening regardless of O2 sensors? Or is it possible that the replacement O2 sensor on that side is no good?

And what is the difference between 1191 and 1193? Is it the side of the engine that sets these two codes apart?

You need a good old fashioned tune up, that means new spark plugs and spark plug wires.
You are getting "rich" codes because of unburnt fuel being sent downstream from incomplete combustion.
Use Kingsbourne, Magnecore or STI plug wires and any spark plug you want.
Once that is done then clear your codes and see if they come back.

OK, I'll try that.

Any idea of the difference between 1191 and 1193?

Thanks for your help,
Phil

No, I have no idea on the difference, I'm not good with codes.

Did you change the front sensors as well? I just did mine today, what a world of difference it made. My old O2's were solid black smudge crud.

So i just finished a tune up. Kingsbourne 8mm wires, new plugs and im still getting p1191. is the safe assumption at this point that my downstreams are bad? If thats my issue im going to be pissed. I already got one ticket in the city for expired inspection, it was due in july. I really dont want another but i also dont want to replace post cat o2's at $50 a piece when all they do is tell me when my cats are bad. The good news is that theyre really easy to get to, the bad news is theyre stupid and i dont want to replace them. I'd appreciate anyone who wants to throw another option at me.

Sorry i've been off a while, i just started a new job, and i'm moving into a new house my wife and i are buying in two weeks. Life has been (continues to be) hectic.

TURF

Just buy used rear O2's, the fronts and the rears and exactly the same on a DI.
So if you still have your old ones throw one in, if not you can buy used ones for about $25 each.

I'm pretty sure that 1191 v 1193 are the same code just on differed sides. You think given how easy they are to get to that it would make sense to swap my rear o2's and clear codes and see if I get an 1193? So id know for sure? Or just bite the bullet and do em both?

Do what I did. Remove your Y-pipe and clean it out real good. With the Y-pipe removed you can inspect your O2 wires and clean up each sensor. My O2's were reading bad, but the CATS were clogged up. No more codes. I had nne codes that resulted from dirty and clogged CATS. The CATS are a horrible design, especially the drivers side.

Yeah, except that's way more work than I want to get into right now. if it's between $50 for two used sensors or dropping the y pipe id rather throw $50 at it. I need to get this thing inspected before I get another expired inspection ticket. And dropping the exhaust doesn't really factor into my crazy busy schedule right now. How did you clean your cats?