After AAMCO finished working on my transmission (http://www.cadillacforums.com/forums/#), which took them about 6 weeks ??? ... I got the car and drove it for about 10 miles, then I got the Check Engine Light and the following PCM Errors:

- PCM 0140
- PCM 0141
- PCM 0155

I cleared the PCM codes several times, but after driving for about 10-15 miles, it will come back again at the Computer rebuilds its data ...

I have been reading about the O2 Sensors (http://www.cadillacforums.com/forums/#) and figured that it might be a grounding problem ...

Can anyone guide me through the steps of reaching the Ground [G109] for the Oxygen Sensors (http://www.cadillacforums.com/forums/#) and whether there might be anything else that I should check ??? ... Some threads indicated that it might be near the Park/Neutral Switch, but I don't know how to reach that spot either (From top or underneath the car (http://www.cadillacforums.com/forums/#)) ...

RHanna,

I wish I could tell you exactly were G109 is but my best guess would be to look around the coil pack at the rear of engine.

Don't forget to check the fuses, the heater circuits are on a fuse in the engine compartment power distruibtion box.

Frank

I had that exact ground wire broken on my 96 STS when I owned it. It is on the drivers side of the motor just below the rear bank cylinder head. I wasn't able to fix it myself as I couldn't get to it, but the dealer fixed it in less than 1/2 an hour...sure would be nice to own a lift.

Thank you for the replies ...

I have checked the fuses and they seem to be fine ...

As for the lift, I have one, but I am not sure if it easier to get to that spot from above or below ???

Does anyone have a drawing of the Oxyegn Sensor Grounding location so that I can stick my hand in the right spot ??? ...

Also, is it just a wire that is conencted to the Firewall or to the engine itself ???

Thanks again !!!

Thank you for the replies ...


Does anyone have a drawing of the Oxyegn Sensor Grounding location so that I can stick my hand in the right spot ??? ...

Also, is it just a wire that is conencted to the Firewall or to the engine itself ???

Thanks again !!!

I don't have a drawing of G109 but the location is: The left hand rear corner of the engine, near the park/neutral position switch.

Its a black wire and usally connected to the frame, engine or coil pack mounting bolt.

I would located the HO2S and follow the harness, there might should be a black wire the harness, trace it. OR disconnect the harness at the H02S connector and ohm the black wire to ground, the reading should be 5.0 ohms or less.

Frank

On my car, it was a black wire connected to the engine block. When I took it to the dealer and explained what I wanted done, the advisor said "we can fix that pretty quick since we have a lift", so I assume it is easier from below.