Hello, I've been working on a 2002 base camaro that I rescued locally (a very high mileage car that had been abused and was just sitting but would start). I've got it running and driving well. I'm throwing a P0140 code for the o2 bank 1 sensor 2 (Post cat). Got everything else straightened out and just assumed bad sensor. Put a new one in and no code! Thought I fixed it. Then it came back on a longer drive. I had the old one plus another new one and swapped those in on the car and all show sensor activity when the car starts. As soon as it comes to temp, all lose activity and stay at 450V and get a pending P0140 code. The sensors seem to be working. All the short range and long range trim numbers are good. Car is running well. The key seems to be car getting to operating temp and I assume this is when the computer transitions from open to closed loop to use the 02 sensor reading but why would it lose activity at the post cat sensor when that happens? What do I check here? There are no vacuum leaks and the temp numbers from the scanner look correct and again fuel trim is great....1%-5% for each bank.

 

check wiring to it and the connector. check to make sure 02 sensor heater is getting power. Check readout of the pre cat sensor. if its off then the post sensor will show fault, maybe switch the pre cat sensor with one of the ones you have