Hi all iv got p0138 and p0037 it's a new O2 sensor and a new 200cell sports cat but I cannot seem to find any faults with the plug or wires, my next step was to re wire the rear sensor from the pcm
Before this the old cat disintegrated with the old sensor in and had the fault bias stuck lean or rich I cannot remember now
Is it the cat flagging up the codes or is there a harness fault
The new O2 sensor came with a plug fitted but it's an after market one
Has anyone had this fault and fixed it or re wired the pcm to the sensor ???

 

What brand is the CAT and the sensor? From reading your post I feel that the aftermarket parts you bought are not serving the purpose...