O2 Sensor Replacement - 1994 FZJ80

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Great write up Scott, thanks for taking the time.

Am I to understand the the Bosch 15728 will not work with the OBD2 (like my 97 TLC) systems? If this is the case, do you know of a planer style 02 alternative for OBD2?
 
alia176 said:
Scott,

Excellent info and thanks for the writeup. I didn't know about the diff style of O2 sensors so I learned something.

Let us know after a few more tankfuls have gone through the system.
Click to expand...

Just FYI, I'm well into a couple dozen tankfuls since the install of the 02's. All is good. Mileage gain is up, but I'm sure no higher than what new thimble style O2's would have accomplished.

80ME said:
just had an O2 sensor pop off of the manifold during a 550 mile trip home. I was able to wire the bugger back on for the rest of the trip but need to properly repair it. 10MM?...what thread pitch and copper?
I just read an owner useing stainless nuts. Is the exhaust stainless, including the threaded posts the nuts mount to? I have concerns about damaging the posts.
Click to expand...

8mmx1.25pitch on the studs. In another thread this debate rages. Mr T. supplied coper nuts from the factory, and they work really well, and are quite tall, helping to protect the stud threads from corrosion. I'm not a fan of SS, or A/S as a rule. Whatever you decide to do, A/S around 02's is to be used with extreme care. A/S contaimination of 02's renders them dead quickly, btst.

p8nt said:
Am I to understand the the Bosch 15728 will not work with the OBD2 (like my 97 TLC) systems? If this is the case, do you know of a planer style 02 alternative for OBD2?
Click to expand...

There are posts here that a planer style 02 on OBDII vehicles will trigger an 02 heater code, as the first couple of years, OBDII measured heater circuit resistance, which changes between Thimble and Planer style.

Directly answering your question, 15728 will not work with the OBD II in your 97TLC. As an aside, I contacted Bosch regarding the Planer style showing as a valid replacement for OBDII in their catalog listings, hopefully they will issue a corretion in their '07 catalog.

HTH

ST
 
Last edited:
Great write-up Scott, nicely done with the basics that even I was able to understand.

If not gas mileage, what specific performance improvement are you talking about? Is it just life and wear performance?
 
Romer said:
If not gas mileage, what specific performance improvement are you talking about? Is it just life and wear performance?
Click to expand...

Planer style O2's as mentioned, move the sensing to the tip instead of the slots in the side. IME and by design, this gives a wider range of exhaust flow vs a thimble style, which varies the number of slots in the side of the probe per application (more flow > less slots). I specifically chose planer style for my SC application, as IME 1/3 more exhaust flow creates a sampling problem. I havent' seen any posts that this is a "problem" for an SC truck necessarily, but I would expect to see decreased service life of a thimble style.

When below boost, the planer style behaves the same as the thimble style. On boost, the planer style will have a wider range of airflow to achieve a proper 02 reading.

HTH

ST
 
Soooo . . how does this increase the trucks performance. Sounds like the o2 sensor performs better or has the capability to perform better as a piece part. Not seeing how this is translated into system performance.
 
Romer said:
Soooo . . how does this increase the trucks performance. Sounds like the o2 sensor performs better or has the capability to perform better as a piece part. Not seeing how this is translated into system performance.
Click to expand...

Hold up! Read the post, I put forth only the *option* is to use the newer, better designed, long life planer style O2 sensors in pre OBD trucks with NO change in performance and no CEL found in the OBDII trucks that gave planer style 02's on this forum, a bad rap.

I see things like plugs, wires, coils, O2 sensors, K&N filters, synthetic oil, oil viscocity, even steel vs copper 02 sensor nuts all the same: An option either works or it doesn't, in this case the change in design gives performance of the *part* to do it's job, and is my interest, performance of the truck is already bolted onto my engine.

Specific to the planer style 02, it *works* as a replacement to the Thimble style 02 in pre OBDII 80's. It will not work in 97> 80 trucks because of the resistance change in the planer heater circuit causes a heater malfunction CEL.

ST
 
Hey Scott Thanks for the Tech. info.

Could you shed some light on the use of two O2 sensors ?
on a OBD1 system, specifically a FJ80 w/3FE duel cat’s

Is this a two bank EFI system, one bank = 3 injectors & 1 O2 sensor?
 
At the parts store they come up with two different O2 sensors
not sure why though. They are both 4 wire,
one is specified as right and the other is left.?


I read you other posts and agree that the FSM is incorrect.
speaking from my experience with the audio electrical schematic
on the 9 speaker system. The FSM conflicts its self and is incorrect
on actual wiring on vehicle too.
 
On my daughters Camry there are three sensors. One on eac down pipe from that side of the engine and then a single one after the cat.

The sensor next to the fire wall was #1 and the one next to the radiator was #2. Of course the error was for #1 and I replaced the one at the rad.

No telling how they come up with the numbering scheme.
 
davisdrafting said:
At the parts store they come up with two different O2 sensors
not sure why though. They are both 4 wire,
one is specified as right and the other is left.?
Click to expand...

Yup, that's noted in post 1. Not sure why bosch does that, but I know 15728 will work for both sides, btdt on my 94 (and 15728 was cheaper by a 15-20 dollars IIRC). I suspect the other side has either a longer or shorter wire harness for the 3FE engine application, or an installed heat sleeve.

I read you other posts and agree that the FSM is incorrect.
speaking from my experience with the audio electrical schematic
on the 9 speaker system. The FSM conflicts its self and is incorrect
on actual wiring on vehicle too.
Click to expand...

FSM has great intentions, especially the shielded wire shown for the 02 sensor wiring: Not in any US truck I've seen.

ST
 
Some quick comments on the Bosch 15728 universal O2 sensors.


After getting what amounts to a "bad ECU code" (83,84,85) and a general O2 sensor error code (21), I replaced my computer with one from a '94.

New computer--no more 83,84,85.
Still had O2 error.

Had one Bosch 15728 universal O2 sensor in the garage. Wired it up and installed it in the outermost sensor position. O2 code is gone.

Later that day, O2 code 21 comes back along with 25 (too lean at O2 sensor). Clear computer, O2 codes come right back.

Decided to replace the innermost sensor with another 15728. Didn't clear computer, but CEL goes away after running for a couple minutes.

I only have 10 or 15 miles on these two new 15728's, but so far they seem to have done the trick. Truck is running very very well. Seems to be shifting smoother (? imagination ?).
If these sensors go the distance, it will be a case of $120 in parts ($60 each) equaling/beating $280 in parts ($140 ea OEM).

Hayes
 
Hayes said:
Some quick comments on the Bosch 15728 universal O2 sensors.


After getting what amounts to a "bad ECU code" (83,84,85) and a general O2 sensor error code (21), I replaced my computer with one from a '94.

New computer--no more 83,84,85.
Still had O2 error.

Had one Bosch 15728 universal O2 sensor in the garage. Wired it up and installed it in the outermost sensor position. O2 code is gone.

Later that day, O2 code 21 comes back along with 25 (too lean at O2 sensor). Clear computer, O2 codes come right back.

Decided to replace the innermost sensor with another 15728. Didn't clear computer, but CEL goes away after running for a couple minutes.

I only have 10 or 15 miles on these two new 15728's, but so far they seem to have done the trick. Truck is running very very well. Seems to be shifting smoother (? imagination ?).
If these sensors go the distance, it will be a case of $120 in parts ($60 each) equaling/beating $280 in parts ($140 ea OEM).

Hayes
Click to expand...

POR, mine have been on for ~5000 miles without any 02 codes. I don't claim they made anymore difference than a new set of 02's. The planer style is the 'new' tech in 02 sensors, and the value for that new tech is darn good (as Hayes points out).

ST
94 FZJ80 Supercharged
 
Just installed a pair into my '94, idles smoother and so far no Code 26. The Autozone guy kept telling me a story that they are discontinued now, and is no longer being stocked... (Superseded by a newer Bosche Part number, version?) My truck idles NICE and Smooth at 500rpm's in drive now... I am thinking that the idle speed should be higher though. $67 a piece for these boys

The Good news is that I finally found my second o2 sensor, another good thing is that the nuts still resembled nuts and came out easily with 12mm wrench Though I was able to use a 1/4" air ratchet on one side which helped. Didn't have to remove anything to access them but I swear that Mr. T could have found a better spot for them... Someone mentioned a custom downpipe with relocated o2 sensors, I am down with the same idea...
 
Nice job on the informative write up... and thanks for disclosing the advantages of the universal type aside from the cost savings.
My downstream was replaced at around 130K with OEM (GM brand planar type) and it was a relatively staight-forward job (yes, same experience with bolts as others) to replace it.

Shortly after passing the Emissions insp. the upstream sensor died. Installed the Bosch planar universal and the chk eng light came on with a "heater circuit (sensor) malfunction" code. Fuel efficiency and performance were improved though, so I got the main wires correct.
Didn't take the fuse out though and I will try that as well as double-check my wiring...

Vahid
 
Not one picture to illistrate the procedure.....shame shame shame!
 
I've read through this post several times over several months as I have an o2 sensor code along with my EGR code. Planning to address both here very very soon. Checking on the Oreillys website it seems that 15728 has maybe been replaced with 15731? Doing a quick google search led me to quickly find 15728's still in stock online, so I am thinking I will go ahead and get 2 here pretty soon.

Was just wondering if there were every any updates on your install? I'm not lucky enough to be running a super charger, so aren't looking for any boosts in performance and am basically interested in this install as a way to save some cash.

Of course I've also been looking into my vehicle history to see if the 'recall' was ever done on my vehicle, but seeing as I've found nothing and I believe the first few years of her life were spent as a leased vehicle, I'm assuming that it was.

Thanks!
 
So an update with my experience with these Bosch sensors. Immediately after install my cel never returned, slight increase in mpg and lower highway rpms. All was well except an acceleration hesitation for the first few minutes the truck ran. Nothing made it better as I tried letting it warm up for varying lengths of time, tried shifting through all the gears, all manner of different starting routines. In the last week I found a good deal on some OEM sensors and decided to go back that route. After install I started the truck and she took right off, no hesitation at all. The Bosch sensors never tested bad, and I'm not sure what would have made them cause this hesitation, but they were definitely the cause. Taking the truck out on a trip this weekend and will pay close attention to any mpg/rpm/etc differences.


Sent from my iPhone
 
Planning to do these style O2 sensors on my 94 with 222k miles that look to be the original O2 sensors.

I know the thread is 3 years old but didn't know how these held up for everyone. Thanks in advance
 
You must log in or register to reply here.

Share this page

Back
Top Bottom