Wow, I think my car finally has an unusual problem. I bought some gauges off of a forum member a few months ago, and one of them was an A/F meter. I'm going to get a wideband soon but figured I might as well install it since I'm getting O2-sensor related CELs.

I tapped into the O2 signal at the ECU to keep an eye on it. It's a one-wire so the sensor just won't get warm enough when I'm idling, which is what I thought was causing the 15 and 17 cels.. But then I went out for a careful drive the sensor got warm enough pretty quick. It looked about like I thought it would since I had the same Autometer A/F in my Turbo II, so after it had warmed up a bit I made some boost to check the wastegate adjustment I had made earlier in the evening.

Then I noticed something weird. Even though the car was fully warm when I started testing, the sensor started reading on average leaner and leaner the longer I drove around. I stopped boosting and just cruised around the block a couple times to see if something the car was doing in boost was making the sensor read weird... and eventually the gauge just pegged at the last lean LED, barely even registering when I blipped the throttle. Everything felt fine otherwise.

I let the car cool in the driveway for a while to see if the signal would come back, but it never did. That would explain the CELs... wtf is up with that? Replacing the O2 sensor again is going to be a ginormous *** pain with how its mounted in the Greddy downpipe, if that's the problem.