99 grand am se 2.4 Oxy Sensor Problem

99 Grand Am SE 2.4

I had a code of P0141 - Oxygen Sensor circuit malfunction - downstream sensor

The boys at AutoZone sold me a downstream sensor and told me it would fix the problem. I put the sensor in and the light still stays on. I used the OBD to reset it thinking that needed to be done and it came right back after the first start. Then I disconnected the negative battery cable for about 30 minutes and it came back again.

I read in the manual that you should not start the car after the sensor install until you reset the computer. Unfortunately I read that when looking for the answer to this question!! Did I permanently embed the code by mistake?

I've checked the plug connection on the sensor cable. Are there fuses that could cause this fault?

What is in front of the wiring after the sensor electrical plug? Anything I can check in the wiring that may have caused the original fault to start with? Can I meter the sensor plug to find faults back in the line and does anyone have any schematics on that plug with values?

PS: The manual shows my upstream sensor should be in the pipe in front of the cat before the manifold connection. There's nothing there???? Any guesses where that first sensor is located?

Thanks in advance for any help.

The upstream sensor is hidden under the heat shield for the exhaust manifold. Remove the three bolts and lift off the shield and you will see the sensor in the manifold on the drivers side of the car. You can get to it from under the hood with a o2 socket.

Welcome to AF ddrdan !

The codes is for a O2 heater ciruit malfunction.
So it's possible that wire for the heater portion is shorted somewhere.
Here's a link with the test proceedures and I think some pics.
O2 sensor check replace (http://www.automotiveforums.com/vbulletin/showthread.php?t=672110)