Last night I replaced my CPS and was going to replace my rear O2 sensor (because I was getting codes P0340 P0141 P1131). I pulled the old sensor, it came out fine, and noticed it's wiring was rubbing on the driveshaft flange. Two of it's 4 wires were essentially cut.
I went to put the new sensor in, it wouldn't thread in more than 1/2 turn then bind. I figured, ok, the threads are crusty so I used a 22mm wrench and applied a little pressure it was still bound and I didn't want to damage the threads so I stopped.
I ended up repairing the wires on the old unit with butt splices then injected the splices with red RTV to seal them. I put some anti seize on the old sensor, it went in fine. My scan tool seems to be reading an output from the rear O2 sensor now.
The new sensor is a bosch I bought from Rockauto.
BOSCH Part # 15718 {Oxygen Sensor}
4 Wire; Heated; Check / Replace Interval: 100,000 Miles; OE Type - Downstream
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1996 Aerostar Shorty Cargo Van (3.0) 198k
easy to get cross threaded because of awkward position
don't need the rear sensor for correct engine operation per PCM.
failed rear sensor only causes a minor code and CEL.
rear O2 only monitors CAT for correct operation
examine the threads on the new O2, triangle file may clean up or take to machine shop and have them chase the threads.
the new O2 sensors don't have enough anti seize grease on the threads for an old crusty rusty exhaust with burned up threads
You can get a tap that you can chase down the threads carefully, to make sure there is no carbon or gunk. It is true that the rear sensor does not participate in fuel management, but if you want to keep your CEL off, you will need it.
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My Rides
1994 Ford Aerostar 4.0L AWD extended
175,000 miles
Fullblown 50 series catback system
590 watt sound system
1990 Mazda B2600i
505,000 miles
Custom exhaust with BearCats high flow converter and a straight through muffler
Custom high velocity intake with AFE ProDry filter
Just replaced a rear O2 Bosch in my sons 96-V6 Mustang. Threaded in very nicely . However when I changed my front O2 on the Aero, the original was very tight to remove & the new (Bosch) sensor was also tight as I replaced it. However, all is good & as I was tightening it I occasionally reversed it 1/2 turn back out just to make sure it was not cross threaded. I think the thread is the same as a spark plug M14 or M12, ISO Metric fine.
BTW my sons CEL never came back on, code was PO156. Old sensor was shot after just 50,000 kms.
Aeroman.
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Green-96, XLT 2wd, 3L Vulcan, from Ontario, Canada
All original powertrain except alternator & starter motor. 292,000 kms & going strong !
front O2 sensor takes most of the head damage from the CAT and air flow is poor there especially on the Aero.
some of the import O2 sensors on the 4 cyls have no air flow
> I ended up repairing the wires on the old unit with butt splices then injected the
> splices with red RTV to seal them.
Most 02 sensors breath through their wires, depending on which wires you sealed, you might have done more harm then good. This is why using grease inside the connectors is a bad idea. But, if you are not throwing codes, it probably does not matter much on the ones after the converter as previously noted.
__________________ The Year 2008 Anno Domini - May it bring a great year of Revelations to you.
>Most 02 sensors breath through their wires, depending on which wires you sealed, you might have done more harm then good. This is why using grease inside the connectors is a bad idea. But, if you are not throwing codes, it probably does not matter much on the ones after the converter as previously noted.
I've never heard of this before. O2 sensors sample the exhaust stream by being stuck into the stream and having the gases flow past the sensing element. The body of the sensor is sealed, as should the threaded fitting. Otherwise, it can get false O2 readings.
Ford (and I'm guessing other auto manufacturers as well) injects grease into the connector pins to seal the ends of the wires in order to prevent moisture from creeping in through them and getting into the electronic circuits.
I've never heard of this before. O2 sensors sample the exhaust stream by being stuck into the stream and having the gases flow past the sensing element. The body of the sensor is sealed, as should the threaded fitting. Otherwise, it can get false O2 readings.
Ford (and I'm guessing other auto manufacturers as well) injects grease into the connector pins to seal the ends of the wires in order to prevent moisture from creeping in through them and getting into the electronic circuits.
The wires coming directly out of the 02 sensor body do indeed have to be open to atmospheric Oxygen, this is where the ref 02 is sampled from, no sealant to be applied on those wires. However at the connector, sealant is O.K..,
Aeroman.
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Green-96, XLT 2wd, 3L Vulcan, from Ontario, Canada
All original powertrain except alternator & starter motor. 292,000 kms & going strong !
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