At the beginning of this i had a intake leak and I was able to seal without having to change intake gasket. Which was giving a P171 code. Now I'm having a issue with my post cat 02 sensor thought it was defective so I replaced it. Still get code although the sensor tests ok on bench using heat test and ohms test. I checked wiring to both 02 sensors the 1st pre cat having .5v but the post cat was very low 0.012volts so I started to trace wires back but they look okay so far then then go into the big harness and back through to pcm. I was checking on wiring diagram and tracing where the wires go to see if I could find any issues. I started to unplug each sensor in motor to see if volts would go up. I found a 5 pin grounding bar attached to top of strut tower as i wiggled it ,the voltage on the post cat went up to about .315 as per the manual voltages on both should be anywhere between 0-.5 volts with ignition key on. I've cleaned the 5pin jumper bar for grounding. Thought i had the problem fixed but i still get the p140 code again. I've even taken the PCM out to check if any wiring was pinched going to it but all ok. Problem with that is that the big connector doesn't have each pin numbered so its a pain to see what the pins are. Ive tried another sensor and still same code....Driving me nuts thanks

 

Update: After numerous tries with ground bonding checking and trying to trace back the wire through mounds of tape and flexible plastic tubing. I took out the PCM and traced the rear 02 sensor that was giving me the P0140/01 code to pin 35 of the big harness which I found out via a online manual. Its got a lot of wires to that plug I grounded the connector pin at O2 sensor plug and then put a small cut into the pin#35 wire before the PCM so I could meter it out. I had the correct wire so I removed the grounding jumper and tested the wire and what ya know it was grounded hence all my troubles. I checked Pin 60 which is the working pre cat sensor and it was clear. So these wires have a shield on outside of cable so I needed to put in a shielded cable and ground the end by PCM and leave the other end floating so as if it picks up any noise it will dissipate to ground and not affect the signal voltage which by the way is only ard a half of a volt. I put it back together and connected up my code reader and read the data stream signals and now its working. Whoa I wont know officially until I drive the car for a bit but I do know that I was getting the fault very quickly now while driving only a short distance with the cooler mornings now....