OK, I just bought my first Cadillac Catera & I guess I shoulda looked before I bought, because it's the 1997 that everyone's always downing. Anyhow, it had the check engine light on & I figured that it couldn't be that bad to fix right? Wrong. It had the codes:

P0141 O2 Sensor Heater Circuit Bank 1 Sensor 2
P0161 O2 Sensor Heater Circuit Bank 2 Sensor 2
P0160 O2 Sensor Circuit No Activity Detected Bank 2 Sensor 2
P1700 Manufacturer-Specific Code (TCM telling the ECM to turn check engine light on, pretty sure the below code caused this code)
P0705 Transmission Range Sensor Circuit Malfunction (PRNDL Input, Found that this is the Neutral Position Sensor)

Anyhow, after searching the forums, I saw that it looked like I just needed to replace the rear O2 sensors. Bought a pair of universal Bosch ones & patched them in (Did a nice job in my opinion, you can't tell them from the originals. Pulled back the sleeve & soldered the wires underneath & used plenty of tape).

I then tried to tackle what I ended up finding was going to be the biggest pain. I knew that there was some sort of transmission problem before I read the codes, because the car would sometimes crawl from a start & would only work right with it in sport mode. After some searching, I found that the Neutral Position Sensor is a royal pain to get a hold of other than the dealership (quoted $320). However, I eventually found that I could order it online from Autozone for $109. Heck of alot cheaper! Once I got it, I found that it was a perfect match to the old one. So, I figured, that this would be no big deal. Wrong! There are 3 bolts holding it on. Two 10mm ones holding the actual sensor & one more holding the shift linkage to the shaft that goes through the sensor. Well, the two 10mm ones came out just fine, however, the shaft snapped off with the nut! I didn't even apply much torque to the bolt. So, to make a long story short, I ended up putting the new one on & decided to just weld the linkage to the shaft (and hope that I don't have to remove it ever again). Tried to start the car & it wouldn't. So, I loosened the 10mm nuts & twisted the sensor a bit (it's made to swivel) & then it cranked up just fine. Took it on the road & it solved my starting in a high gear problem just fine. Also got rid of the last two error code.

So, now I go back to the emission place & find that after all this that the first two error codes are still there (even after clearing them). Could there be something other than the O2 sensors that is causing this? Is there a seperate sensor for the heater circuit? I figured that it was just a part of the O2 sensor. Please help me someone, because I can't get my car legal until I can get the check engine light off (St. Louis is strict about the emissions & goes completely by the OBD-II codes on '96 & newer vehicles).

Ok here's my story. I too bought a 97 Catera about 5 months ago now. It too had the check engine light on. Mine turned out to be the spark plug wires, but here's my point. Here in North Carolina we also have strict codes, and you cant get a car to pass inspection if there are any stored codes in the computer, even if you turn the Check Engine light off. I took mine down as soon as I fixed it and cleared the light, but it still had stored codes in it, so it failed. They told me you had to drive it for about 30-40 miles before the computer would reset itself, and get rid of any stored codes. So I drove it down the interstate for a while, and I carried it back and it passed, stored codes were gone. I don't know how far you've driven since you turned off the Check Engine light, but it does take a while for the codes to completely clear. I hope this helps you, and by the way, I've found it wise to invest in a decent Code Reader tool, $69 at Wal-mart, you'll need it with this car...lol. Good luck!

I actually cleared the codes myself (verified). Unfortunately, I still can't just go back until the computer gets any new codes, which is why I have the two O2 heater sensor codes. I drove the car about 30 minutes after clearing them & those two came back. So, it's not in the history, but actually something that's wrong. I'm hoping that it's something other than the O2 sensors themselves, because I just bought them & would hate to find that I have to get different ones.

OK, I've scoured Google & found that the possible reasons for these codes is:

-Blown Fuse or relay
-Short in the harness
-Water in harness connector
-The ground or power wires are not connected somehow
-Low Battery Voltage
-Poor electrical connections from PCM to the O2 Sensor
-The O2 heater is just plain bad
-The PCM is bad or faulty

Gonna check tonight. Hoping for the fuse or relay. If it ends up being the sensor, I'm just going to build a simulator, since I know that they are good. From what I can tell, the simulator is just a resistor (around 10-40 ohms) between the two heater wires (white ones), which is what you should read if you measure the two white wires on the sensor.