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rear o2 sensor


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because i didnt have the foresight to replace it when i was litterally kneeling in the engine bay drilling holes through the exaust flange with the engine out a few weeks ago. got it running and im throwing codes for the rear o2 sensor along with a random misfire [p0300]. i am hoping one will fix the other.. be we shall see. anyways, having a very hard time accessing it because of the two heater core/recovery tank pipes that piggyback the bank 1 valve cover all but completely prohibit access from above. cant seem to get my o2 socket on from underneath either because even though i can touch it, i cant get a thumb up there WITH a finger. has anyone replaced this nightmare before? or does anyone know what the FSM says the procedure is? i am downloading a shop data program illegally (shhhhh) but its going to take like 2 more days to finish the GM cd's. any help before then would be very much appreciated :]

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so i haven't gotten any replies here but since i did search so long for an answer (as with previous threads :)) i figured i'd post what my came up at my buddy's dealership's eSI system just in case anyone was looking for the same thing.



Remove oxygen sensors with engine temperature above 48°C (120°F). Otherwise, oxygen sensors may be difficult to remove.

Take care when handling oxygen sensors. The electrical connector and louvered end must be kept free of contaminants. Do not use cleaning solvents on sensor. Do not drop or mishandle the sensor.

A special anti-seize compound is used on oxygen sensor threads. New service sensors should have the compound already applied to the threads. Coat the threads of a reused sensor with anti-seize compound P/N 5613695 or equivalent.


Raise vehicle and support.

Support rear of powertrain frame.

Four frame bolts (# 2 and # 3 locations).

Lower frame no more than 3 inches.

Rear oxygen sensor connector.

Rear oxygen sensor at rear exhaust manifold.


Rear oxygen sensor at rear exhaust manifold. Tighten Oxygen sensor to 41 Nm (30 lb. ft.).

Rear oxygen sensor connector.

Raise frame.

Four frame bolts (# 2 and # 3 locations). Tighten Frame bolts to 100 Nm (74 lb. ft.).

Lower vehicle.

going out to the garage right now. sounds like a pain in the *smurf* but at least i have plenty more to do aside from that :)

thanks anyways guys and may god's love be with the notion of a bad o2 sensor being the culprit behind my p0300 :)

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Its a piece of cake and the easiest one to replace, it sounds like your heater pipes are not in place in the brackets. I would just move the pipes out if the way, I have changed two in that location, very easy

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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nah the heating pipes are there.. wouldn't have asked the question otherwise :]

it's definitely not the easiest one to replace either. i'd say it ranks fourth easiest to replace.. right after the three you DON'T have to drop the subframe to barely be able get a wrench on.

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