The CEL that won't die

[Perfectlap]

^Except for the first 02 sensor (my idea), we did not change those parts because of the CEL itself, they were replaced for other reasons (different CEL codes I can't remember right now). I guess the way I wrote my initial post made it sound like I was replacing parts just to clear the codes, but that wasn't the case.

The O2 connections were checked before the decision was made to replace all four sensors, so the code itself doesn't make sense to me. I don't know how exhaustive they were about looking at the wiring in general but they're pretty thorough on these things, particularly the mechanic who did the work. Also, there was a leak, a very bad one on the old aftermarket headers which were badly cracked on both sides, so new aftermarket units went in this year. What I'd like to know is why the CEL seems to be tripped by jarring to the underside of the car.