I've been getting a P0420 code lately. When I check the Oxygen sensors I get no data. I'm using the Auto Enginuity scan tool on a 98 XLT (100,000km).
I was looking at the wiring diagrams last night and it looks like the O2 sensors connect directly to the PCM. So, I'm wondering if there is a possibility of a problem with the PCM? I have yet to crawl under and backprobe the actual sensors. Just looking for some possibilities in advance. I can't see all four sensor going kaput at the same time.
I've tried the scan tool on a couple of other cars and I was able to see the sensors behaving properly.