Since i replaced my front o2 with a new one, about every 200miles i get a P0137 Rear O2 Low voltage code, does this mean the rear o2 is bad? also it is not in the main exhaust stream, Installed the spacer to pull it out after i put a "test" pipe in to replace the cat for the time being. hasn't been an issue until i replaced the front o2.

 

anyone.?