Downstream O2 sensor on 4.2... tips on disconnecting?

[budwich]

Since I was under the truck chasing the drone, I thought I would look at replacing the downstream 02 sensor since it throw a p013b code every so often... strange code but it is what it is.... I would think it points more to a sensor issue that an engine / emission problem... I think. There is almost no room to reach / manipulate the plug to disconnect the sensor. Is there some tip to getting at this and disconnecting the connector? or is swearing and some awfully small / long arms required? I haven't even attempted to unscrew the sensor yet which is probably another fun story on a 10 year old exhaust system.
Thanks.

 

[gmcman]

Use this tool with a 3/8 breaker bar.



I would soak the sensor threads with PB blaster the night before. Before you remove the sensor, I usually start the engine and let it run for about 1-2 min. This may or may not release some pressure on the sensor threads ...either way, has worked great for me the few times I've changed them out.

 

[Mooseman]

I've had bad luck with sensor sockets, which are 7/8". They are just a little loose on the hex and strips them if it's stuck bad. I've had great success with using a deep 21mm deep impact socket that I cut a slit in for the wire. It fits tighter and won't round the hex as easily.

Heat is your friend. If you have a propane torch, heat around the sensor on the bung on the pipe to expend it a bit. In some really bad cases, you may need an oxy/acetylene torch to get it red.

 

[budwich]

I have the 22mm o2 sensor socket... my main problem is how to get the connector disconnected. I can't manipulate my one hand to be able to reach into the "little" space and cause the disconnect.

 

[gmcman]

These are my goto O2 sensor tools.



Sidenote.. The picks are just an overall necessity IMO for many other areas of the vehicle.

I use the body panel tool to remove the O2 sensor connector from the mounting location, should pry right out.

There may be a secondary catch on the connector, but once you get it loose, you will then get slack to pull it down a little. Then I use a pick to release the tab.

@Mooseman that O2 sensor socket pictured above is pretty much what you described...it's thick like an impact socket with a slot cut into it. Has added leverage being slightly offset, gets into tight areas easily.

 

[Mooseman]

Maybe you would need to drop the tranny a bit by removing the crossmember. Might give you enough space to get your hand in there. I don't remember it being that tight and I have huge meat hooks.

 

[budwich]

Maybe you would need to drop the tranny a bit by removing the crossmember. Might give you enough space to get your hand in there. I don't remember it being that tight and I have huge meat hooks.

hmmm something is amiss then... as my arms are "pint size" and yet getting between the frame and the tranny is difficult while trying to manipulate the connector. will have to try again... maybe adjust my body angle. I am trying to do this while lying on the ground with the vehicle ramped.

 

[Mooseman]

Although I don't remember, maybe mine was off its holding perch where the Christmas tree goes into to hold the connector.

 

[budwich]

These are my goto O2 sensor tools.

View attachment 89447

Sidenote.. The picks are just an overall necessity IMO for many other areas of the vehicle.

I use the body panel tool to remove the O2 sensor connector from the mounting location, should pry right out.

There may be a secondary catch on the connector, but once you get it loose, you will then get slack to pull it down a little. Then I use a pick to release the tab.

@Mooseman that O2 sensor socket pictured above is pretty much what you described...it's thick like an impact socket with a slot cut into it. Has added leverage being slightly offset, gets into tight areas easily.

Yep got everyone of those tools... I am thinking maybe some form of "slide tool" like a long "wide blade" scew driver that can push up on the retain clip "lever" then I can just pull down of the pig tail to pull / disconnect from there. I will certainly try different attacks as surely it can't be that hard... gm would never do a design like that...

 

[mrrsm]

A few years back... before I got to the point of damned near getting Carpal Tunnel Syndrome from honking down on the narrow handle of a Huge Crescent Wrench... I picked up THIS tool and took it to the Next Level by cutting off a decent length of the Rubber Covered Hollow Handle(s) from an old pair of Garden Loppers (...naturally, any similar piece of pipe will do here).

By using these two items in combination, I've been able to remove O2 Sensors from then on to this day with ease. The flexible split socket head and the ability to alter the length of the 'lever' by telescoping it for varied situations provides the maximum mechanical advantage needed... without having the tool slipping off and rounding off the Hex faces on the sensors:

Amazon.com: EWK 22mm 7/8 Inch O2 Oxygen Sensor Flex Head Wrench Removal Tool: Toys & Games

Amazon.com: EWK 22mm 7/8 Inch O2 Oxygen Sensor Flex Head Wrench Removal Tool: Toys & Games

www.amazon.com

 

[gmcman]

@budwich I went out and took a look, I was able to set the frame on a Jack stand, crawl under and reach my hand through here....right behind the transfer case.



The sensor was easily reached by my hand...have you tried that route?



The rear looks like it doesn't need the body panel tool, just the front one.

 

[budwich]

thanks a bunch... I will give that a shot tomorrow. In the past, I have tried from the side / front access as I can readily see the connector but maybe the back area is "easier"... I was basically following the cable from the sensor towards the connector.

 

[budwich]

OK.... partial success. The great hint about coming from the back just in front of the transfer case allows the right hand to get around the tranmission frame support to reach the connector while the left can squeeze by the transmission / body to provide additional "fingers". Getting the safety "pin" out so that the tab can be lifted was hard but eventually came out. The plug could readily be disconnected thereafter.

success is limited as getting the actual sensor off (compared to the front) appears to be tough. My 22mm o2 sensor (as pictured) is indeed 22mm as I also have a 7/8 (22mm) that "they" try to market as the same but it is pretty much useless (too loose). My problem now is the 22mm "springs" enough (even though it appears to be some form of casting... but slot in the wall probably weakens the body a bit) that it eventually will / is rotating on the nut head. :-( I have hit the sensor with crc freeze off... will give it some more time. clean it up and give a propane torch with its "breath of fire" a try.

I may try a box end 22mm wrench after cutting off the wire end... might be the best solution... IF I can find a 22mm in my tool collection.

 

[budwich]

well I have do "uncle" on this. The thing won't budge and I don't want to strip the nut so I need to get it to a garage that has more heat capability as the propane torch doesn't appear to get it done even after a good 5 minutes and glowing sections of the muffler pipe. I cut the wires and used a 22mm box with a pipe extension and still no go... but fear of stripping was greater than muscle as the thing is in a bad place where they might have disassemble the pipes to get a stripped sensor out. Hopefully, with proper heat and such, a garage can make quick work of it... but you never know.

 

[Mooseman]

I have used my oxy torches so many more times than I can count. Pretty much a necessity in the rust belt. A 12 point box end wrench is worse. The shop should be able to get it out.

 

[budwich]

well "uncle" turned into to an "aunt".... :-0 After thinking on things more during sleep, I figure I would give it one more try this morning. This time torching the o2 sensor and area (that was mostly reachable with flame) til red hot ( about 5 minutes). The secret (at least that is my guess) is to put the box end wrench in the freezer before this so that it is at below freezing. Get the cold wrench out and the "rest is history". Basically, it appears that the mass of the cold wrench has enough thermal cold to basically "thermally shock" just the nut of the o2 sensor. A slight tap on the wrench with a hammer and the sensor loosen and was easily wrenched off. That's my story for now... although it could have been all the previous attempts at heat and wrenching and crc freeze off, etc from the other day.

The point with the cold wrench is there less chance of cracking the muffler area than watering which can't be controlled as easy. Also in the case of the o2 sensor, the nut and threads are relatively close so the thermal shock doesn't have travel far to have an impact.

Hopefully my replacement sensor will stop the p013b coding as it was getting trying have to reset codes on a regular basis. Lucky for me, ontario dropped the "emission checks" last year.

 

[budwich]

on a somewhat related unrelate note.... I had been trying to get the differential fill plug out of the rear end. Got a "made for" male 3/8 socket as the normal 3/8 male socket wrench end is somewhat rounded and basically only helps to round out the female plug... :-( Even with the proper male 3/8 socket, it still wouldn't budge and was heading to a round female plug... :-( I was starting to resign myself to drillling a 3/8 hole in the plug and using a self threading bolt as a plug once I changed out the fluids (of course once everything is cleaned out in terms of metal particles from the effort).

I decided to give my recent "discovery" of "thermal cold" on a hot bolt / nut a try. Put the 3/8 (1/2 drive) in the freezer (15 minutes), heated up the plug for about 2 minutes ... was some what concerned about cracking the casting. Tapped the frozen socket into the female plug. Hit it with the impact wrench and voila... it spun out like it was never even tight. Another win!!!!

 

[Mooseman]

viola

Fixed that for ya. It's my pet peeve