08 Mazda5 P0134 mystery
 

Hoping someone has experienced this and/or knows what's happening. About two years ago we had to replace TCM. Shortly thereafter, this adventure started. P0134. Replaced 02 sensor. Also replaced battery and battery cable. Still P0134. Replaced 02 sensor again. Very rich fuel smell, P0134 popped up again. Took to mechanic shop. They said the vehicle was losing communication with PCM periodically (not to be confused with TCM which we'd replaced before) and recommended new PCM. We replaced PCM. P0134 pops up still. Each time codes are cleared and then it comes back. Anyone have any advice?



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We have confirmed that the O2 sensor is seated properly.

Odds of this whole thing being something to do with a wiring harness?