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I've searched using different wording and still don't have a definitive answer. I bought a 1989 F250, gvw 8,500+ 5.8l. The y pipe was a dual pipe setup all the way to where the cats would have been. It had two oxygen sensor bunges but only the rear most one was plugged in to a harness running down the driver side frame rail and crossing over the transfer case the forward most had a O2 sensor plug in place. On the passenger fender is a connector that an O2 sensor will plug into so I connected and O2 sensor and plugged it into the Ford most bunge because I kept getting a fault code for O2 sensor not switching. Due to a hack job by the previous owners on that y-pipe I replaced it with a similar y-pipe that had only the rearmost bunge. Can I get from somebody a definitive answer on how many O2 sensors my truck should have, because I've seen threads that say 2 o2 sensors, I've seen threads on various forums that say one sensor with the harness running down driver side and crossing over the transfer case and I've seen threads where the harness comes down to passenger side. That's the problem with forums like this you learn a lot of great information but there's also a lot of conflicting information that never gets straightened out. I would like to eliminate this fault so I would like to know how many I'm actually supposed to have. And if that answer is only one O2 sensor which harness do I plug it into one running down the driver side and over the transfer case or the one that runs down the passenger frame rail. Thank you in advance for providing me an accurate answer to this issue.
More information needed.
Is the engine original to the truck?(check door jam vin)
Is the EEC original to the truck?(may have to pull it out to verify)
Is it Mass Air Flow(MAF) or Speed Density(SD)?
Some MAF had 2 O2 sensors, and I think SD has only 1.
My SD truck has 1 O2 sensor installed right at the junction of the Y-pipe before the cats, single exhaust.
single O2 sensor, only trucks with 3 sensors are OBD-2 or maybe california models. The O2 harness connects to the engine harness behind the battery, should be a 4 wire connector .
How do I verify if engine is original or at very least a correct Vin code matching replacement? Pretty sure eec is correct. I pulled it once before for something. Ben 89 it is still speed density. The only O2 sensor that was in this when I bought it what is mounted to the rear of the y-pipe which was to individual pipes driver side pipe come over but never connected into passenger side there are two o2 bunges on that ypipe. only the rearmost was being used. the front one was plugged. my wiring harness for my O2 sensor runs down the driver side and crossed over the transfer case and I'm pretty certain it's original in its location. all that wiring harness and everything doesn't look like it's been messed with or altered.
Position number 8 in your VIN will tell you what it had stock for that cab's vin.
Engine Code
Y = 6 Cyl 4.9 Liter EFI1987-1993
N = V8 5.0 Liter EFI1987-1993
H = V8 5.8 Liter EFI1988-1993
G = V8 7.5 LiterEFI 1988-1993
Now to find the engine date code will be somewhere near the starter, on the right side of block.
If the engine is from the 80's, the code will start with "E", and if from the 90s, the code will start with "F".
The only way to for sure tell if it is NOT stock, you will have a 90s engine in your 80s truck, or your VIN will be something other than a 351w
first pic-- is your O2 sensor that should be a mini H-pipe with O2 bung welded in, second pic-- I believe that piece is just to keep pipes from touching/rattling against each other, not a 2nd O2 sensor mini H-pie and O2 sensor
Thanks for the replies. In the pics. The o2 sensor was screwed into the rear stop touching fixture. I confirmed both pipes are drilled, allowing the sensor to get exhaust gases. My harness feeding from the driver side wouldn't even reach for connecting an o2 sensor to the front opening. After Sunrise I'll test the O2 sensor for both these changes as it heats up. If my truck is only supposed to have one sensor, am I correct in assuming it would be a switching sensor since I do get a fault code saying it's not switching?
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