Any advise? Trying to get through emissions...
99 V70, std, non-turbo - chk engine light came on @3-4 months ago. Now need to pass emissions. Both O2 sensors were bad (had P0130 & P0136) - replaced both. Code P0136 returned & rear reading is twice front. Tested & everything going into cat good. Propane test good. Replaced cat with Bosal & still same problem - rear O2 reading twice front - P0136.
Umm....help!!?

 

Did you ever figure out how to prevent the code from returning?

I'm in the exact same position with my 1999 V70 non-turbo. I had codes p0135 and p0136. I replaced the front and rear O2 sensors and the J-hose on the evaporative canister (which was completely severed). P0135 went away but P0136 comes back after just a few minutes of driving.

I'm been using an OBDII scan tool and have seen that the voltage on the secondary O2 sensor is normally around 800-900mV, but a sudden change in engine speed causes it to drop to 0V for a few seconds and then jump back to the 800-900mV range. This behavior seems very strange. Does anyone know if this is normal?

Also, I watched a few times and saw that the CEL light comes in sync with the drop from 900mV to 0V.

Does anyone have any ideas about this?
Thanks!