O2 sensors

I recientl bought a 96 Saturn SL with 140K and I've fixed most of the minor problems, but there are still two that I can't figuire out. #1 - the error codes tell me that both O2 sensors are not working, but I just replaced them with bosch OEM types. I tested the sensors and I get the expected voltage outputs on both. Is there a fuse that I am missing or possibly a bad wire? I was going to try to trace them back to the PCM and test them again from there, if possible.
#2 - the cooling fan never turns on. When stuck in traffic, the temp gauge sometimes climbs almost into the red. I've replaced the coolant temperature sensor, checked the fuse and relay but still nothing. Since the temp gauge is moving, it seems like the sensor is working. The fan does come on with the A/C. Is this another sensor whose wires I can trace back to the PCM and test there? Could the PCM be bad? The car gets poor mileage (20 - 24) and starts to blow smoke when the engine gets hot. Synthetic high mileage oil does help with that. The engine good, no leaks, with plenty of power? I'm stumped?

I think you will find this link (http://www.saturnfans.com/forums/showthread.php?t=41736) and the site very informative.

Good luck and let us know how it goes. :smile:

What error codes?
Welcome to the forum also.

Thank you, I've already picked up a lot of info.
OK, here's what I'm getting now: THis is from the Emmisons Center's printout
P0131 O2 Sensor Circuit Low Voltage (bank1 Sensor 1)
P0134 O2 Sensor No Activity Detected (Bank 1 Sensor 1)
P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
P0171 System too Lean (Bank 1)
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P1133 Manufacturer Specified Code
These are all new codes that showed up after a few days of driving. I had the AZ guy clear out all the old ones after I replaced both O2 sensors. They were both heavily coated with 140K miles work of carbon.

Have the codes reset?

They told me at AZ that they could clear out all the stored error codes.

They told me at AZ that they could clear out all the stored error codes.
I am glad they cleared the codes at AZ. I'm just curious if any of the codes came back after you replaced the O2 sensors.

When I originally had AZ pull the error codes there were 22. I used the list and did a lot of repairs. I changed the plugs, wires, air filter, oil & oil filter and replaced the coolant temperature sensor, coolant leval sensor and both O2 sensors. The coolant level light stopped blinking and the Check Engine light went out. Then I had AZ clear out the codes and I drove the car a few days. The warning lights stayed out, so I tried taking it for another emmison test. This list I gave you is what just showed up at the latest test.

That weird that the emmisions would pull those codes but the light has not come back.

yes I know, after I failed the test, they told me to go into the office. They gave me an OBD - Repair Diagnostic Report (RDR) with all the codes and descriptions on it

its like the sensors aren't even connected. if you have a digital multimeter, check for 12 volts to the pink wire for the rear O2, and for ground at the tan-white and black-white wires. also check the eyelet connectior attacted to the engine block above the starter, i think there should be 4 wires there.

http://www.saturnfans.com/forums/attachment.php?attachmentid=4071

woah, First of all O2 sensors operate between 100MV-900MV. There is some tolerance but yours are new so they should be pretty close to that. With the key on engine off the O2 sensors should be at 450 MilliVolts. No way in hell does an O2 sensor ever see 12 Volts unless its heated. In which case only the power wire should be around 12 Volts. The signal wire should read only 450MV with Key on engine off, and check the ground man. A bad ground could be the problem of all those codes. check resistance of the O2 sensor ground wire all the way up to the battery negative terminal. It shouldn't be more than 100 MilliOhms. anything over that is a crappy ground. Make sure you hook your multi meter up in the right mode and range, dont wanna smoke it do ya? Its pretty hard to get that smoke back in ya know? The O2 sensors tell the PCM when to start EGR by the way. If they arent working then the system never sees closed loop operation and the EGR never starts and closed loop my friend is where you get your gas mileage. Check the ground.

don't worry Tek, the pink wire is the rear O2 heater circuit.

It works !!! I finally got a chance to crawl under the car this weekend and take a look around. I found two connectors, each with two wires, that were not connected and the lower oil pressure/temperature sensor wire was also dangling. This was probably from when the previous owner replaced the starter motor. After I reconnected everything, the car ran much smoother, was more powerful and the raw gas smell was gone.
My son called me today, after driving the car about 75 miles and said the gas milage has jumped dramatically and the check engine light came on. I think that is a good thing, since I didn't have the existing error codes cleared. One of the notes on my last emmision test failure was that my check engine light was inoperative or dissabled.
My next plan is to take it back to AZ and have the error codes read and cleared again and if the light stays off, to try the emmisons test again.
Thank you all.

Still Confused??? The car is still running better than ever and getting over 34 miles to the gallon. I took it to AutoZone Saturday morning to clear the error codes. I expected the check engine light to go out, but it didn't. They said it sometimes takes 15 minutes to reset? Anyway, we drove it around all day, but the CE light never went out. I took it back to AZ Sunday morning and had them check for new errors, but it came up clear. So, now what can I check? I thought I might try disconnecting the battery overnight, to clear out and reset everything? Any other suggestions?

remove the PCM B fuse with the engine off key off, wait 15 seconds. then reinstert. drive for a while if the light doesn't come back on, you are all set.

you can reset your PCM, but usually the Engine light will go off after a certain amount of drive cycles with no sensor failures. A drive cycle is when the engine warms up and goes into closed loop then the car is shut off and it cools back down. It could take a week of driving it before the light goes out. there arnt any more codes so drive it for like a week then check for codes again if its still light. Sound Good?