ok i've been getting pretty bad gas mileage as of late (about 12-14 mpg highway) so i decided to buy another pre-cat o2 sensor. I first scanner my computer with a obdII scanner, only code that showed up was p0325, which i've been having for months and can't get rid of it (that's another topic), but on the readiness i/m monitors, the ho2 sensor kept saying not ready. I changed it with a new ac delco ho2 sensor off ebay, scanned it again, its still flashing. The manual says that it may take a few drive cycles for the diagnostic self check to complete its scan/requirements for the monitor to be complete. Next day i scan, i get a green light on the emissions scan, and the monitor was complete. All was good.....till 3 days ago, all of a sudden, i scanned it and the ho2 sensor monitor is flashing again, and the emissions light changed back to yellow, which was the way it was b4 i changed it. I took it to a local shopped yesterday to hook it onto its computer and they told me that the sensor or the connection was bad and that i was getting a p0134 which is no ho2 circuit activity, so i bought a bosch ho2 sensor and they put it on, rescanned it, and they said it was working, but the monitor still was saying not complete. when he took the old sensor off that i had just put on a few days prior, we noticed that 2 of the wires were loose (i didn't crimp the connections tight enough, had to cut off adapter from old sensor and put it on it). I checked it again this morning, still flashing, got mad and put my old one back on and am taking the new one back. i've driven it about 30 miles and still not complete readiness, it did not take this long last time, anyone have any ideas?? i've checked the wires and the wire harness, and the pins in the adapter, all look good.

 

anybody???

 

You might get more help if people know what model year and engine and transmission you have. You could put that into your Profile signature so that you wouldn't have to put it in every time like mine is at the bottom...

What you might have to do is check your sensor wire harness from top to bottom with a Digital Volt Meter to see if the wires are good all the way to the computer connections...if not then you will need to start to hunt down other options....

Maybe have the codes and freeze frame data deleted to see if the code returns...

Good Luck

 

thanks for your help and advice, but the problem is gone, i had to drive it a bit longer it seems.