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Vehicle Speed Sensor: round or square?

10K views 34 replies 6 participants last post by  EZR718 
#1 ·
Greetings fellow travelers!

My better half and I own a 2006 Taurus SE. Getting close to 194k miles. With just the basic maintenance over the years I must say this has been a heck of a good ride.

But some time last week I was alerted about an issue that I really don't like. Cruising downtown, going 20 to 25 mph, I all of a sudden noticed that the speedometer went wild, swinging back and forth between 20 and 30. At the same time the transmission was shifting all over the place. Didn't last long, as I only had a 500 ft drive to do. On my way back (I was 45 miles from home) that never happened again.

On two more trips out of town I've noticed similar symptoms, once at around the 60 mph point, and again today at the 70 mph point. And in both cases turning off the cruise control helped, by me having better control of the speed.

For the regulars around here: yes, I've done my share of reading here, thus far. It's always been my first stop for info, after running into an issue, and after running into the fiasco that is the local Ford dealership.

And so it seems that our problem would be the vehicle speed sensor. I'm no hero when it comes to replacing car parts (almost pooped myself replacing the starter a while ago!) (no, just kidding!) so I'm leaving this one to someone else. The one and only shop around here is known for overcharging customers (no competition!) so I will have to take it out of town (at least a 70 mile round trip).

I just happened to be at the "local" Autozone this evening, after going to the bank; and wanted to buy such a vehicle speed sensor. But it turns out that they have two models: one with a round(ish) connector, and another one with a square connector. Yet, looking at those on their website (PN 917-657 and SU8798) it tells me that both "fit your vehicle". That can't be right, right??? The price difference is a bit baffling too!

O'Reilly has both the Dorman and a BWD part, for the same price, and both with a round(ish) connector. NAPA has the one with the non-square connector, and so does Advance. Is Autozone just dead wrong on this one with the square connector, and the extra $150??

I certainly wouldn't mind saving 150 bucks. Any guidance, please?

Thank you,

Erik
 
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#2 ·
Been 16 years since I replaced the VSS in my '97 Taurus (3.0 L Vulcan), but I remember there being two. It depended on the transmission coupled to your engine. Mine was AX0D (or AX4S), which ended up being the narrower barreled sensor, with no plastic gear on the end. Had to transfer the plastic gear from the original VSS to the new one.

The transmission type was embossed/stamped on the transmission pan underneath the car. I think you can also tell from the VIN#
 
#3 ·
You really have an OSS, which is a variable reluctance sensor, much like an ABS wheel sensor. In general, such sensors are very robust and very rarely fail. I would be inspecting the OSS electrical connector for damage, corrosion, etc, and inspecting the wiring harness from the OSS to the PCM for damage, rub thru, etc.

FYI, you have an 4F50N transmission.
 
#5 ·
VSS = Vehicle Speed Sensor
OSS = Output Shaft Sensor

They essentially fill the same role, but the technology that achieves the end goal is different. The 4F50N uses an output shaft sensor, as Jeff said. It's actually rather easy to find the harness for this sensor. The sensor itself is tricky to locate, as it has to be done entirely by feel for the most part. But the wire and plug is right below the transmission dipstick.

As for what to buy for a replacement, the sensor you're looking for looks like this:

 
#6 ·
Thanks for that info. That (at least on my screen) looks identical to the (Dorman) part that Autozone has in stores around here. I'll pick up one of those tomorrow. And thanks for the hint regarding the location of the little critter!
 
#7 ·
No problem. The wire leads to the sensor, but it's not apparent at first, since there's a splash cover that holds it in place. You'll have to feel for and remove the 10mm bolt to get that cover off, and the sensor out. Have fun ;)

And check the wiring while you're there!
 
#9 ·
I finally got around to doing this tonight. I'd ordered the BWD part (thank you, sousa632) from O'Reilly's last week while I was in the store; but they messed up and ordered the wrong part. So I had to do it all over again; and this time I have the proper part. And it was time; because with the TX temps going up fast I noticed that the issue came up much faster, even after driving it at low speeds around town for 20 or 30 minutes.

I had a few hours of time this afternoon; so I popped the hood and got to it. Having the new part in my hand and looking at the relatively short wire I knew it couldn't be hidden that far. Found it. Thankfully my arm was long enough!

The 10 mm bolt ice445 mentioned turned out to be an 8 mm bolt. Had me going for a while; because the 10 mm socket didn't fit. I thought the bolt head might have gotten damaged, until I went smaller and smaller. No worries, ice445, typos happen! :)

The sensor came out easy enough, and the splash guard with it. I didn't see any damage to the sensor housing itself; but I did see that the housing and the cable sleeve had separated. The wires inside were glistening with oil (see picture). Also, the mating connectors on that arm were covered with oil and dirt. Yup, I got an oil leak someplace!

After removing the old one I installed the new sensor. Again, nothing to it. I put a tiny bit of transmission oil on the new sensor's gasket; I'd read somewhere that that would help inserting the new one. I put my weight on it, it snapped in place, and then all I had to do was line up the bolt holes, the same with the splash cover, and then put the bolt back in. Easy as pie. I put the strain relief on top, snapped the female connector into the bracket, and plugged the male connector back in.

By that time it was 96 degrees outside. I decided to top of the fluids, look for an evap leak (which it seems to have) but soon had to call it quits. The sun was killing me, I was soaking wet and getting a headache. I wiggled and inspected some (suspect) hoses and reset the DTC to see if that would do something. And then I went inside to cool off, and didn't come back out until about 8:30.

So I decided to take it for a test drive. As soon as I got out of my driveway I figured something was wrong. My driveway, and the road, are downhill; and I get up to 10 or 15 mph without even trying. But, horror, my speedometer read ZERO mph!!

I drove around the block, with the RPM at about 1600, way too high for that speed, and parked it back out front.

Ugh! :angry:

My first thought: I may have gotten some sweat into that male connector. So I unplugged the connectors, made sure they are pointing downwards, in an attempt to let them drain overnight (if anything is in there at all).

Second thought: perhaps it wasn't wise to clear the DTC codes?

What are your thoughts, folks?

Thanks,

Erik
 

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#10 · (Edited)
Sorry about that, I was remembering the size wrong. And that separation between the sleeve and casing is actually normal. The oil that's on it would either be from a leaky valve cover or a burping trans dipstick.

So I looked into it on my diagram. The OSS feeds directly to the PCM over the dark blue/yellow stripe wire. You need to trace this wire all the way back to the PCM to figure out if there's a break. A scan tool would also be helpful here to see what the PCM is actually seeing for output shaft speed (if anything). Worst case scenario is a failed driver in the PCM for this circuit.
 
#11 ·
Thanks for your very quick reply; I just got the email.

It seems you've edited your post by now; initially you mentioned ForScan. I don't have that, sorry, although I've seen it mentioned in the forum (stickies, I believe). What I have is a very basic reader, without memory or anything, and it doesn't do any "live" reading.

I'll see if I can trace that dark blue/yellow stripe wire back to the PCM. I have to find the PCM first; but I'm sure I can find that by searching this forum.

In the meantime: what do you mean by "failed driver"? What kind of driver? As in (computer) software driver? Or an electronic component on a circuit board?

Thank you!
 
#14 ·
It's hot!

Before I started doing anything else I decided to put the old OSS back in, just for the heck of it. Easy sanity check, so to speak.

Drove it around the block, with the engineering test mode on and set to read vehicle speed.

Zero mph...

So on to the wires. What I did notice right away is that the back of that plastic covers clearly shows that it has gotten wet, and several times at it. There's water stains all over the place.

Anyway. I'm out looking for that dark blue/yellow stripe wire. Does anyone have a sweat pan?
 
#16 ·
I haven't found it yet. I was expecting to see a whole lot more wires down there. All I see is what's in the pics below, under and behind the glove compartment. And none of them look dark blue/yellow.


What am I missing? Are there any other covers that I need to remove first?
 

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#23 ·
OK, thanks again. I got distracted by visiting family early this evening. By the time they left it was dark; but I did have a quick look at that cowling. Seems possible, but not after dark with a simple flashlight.

That cowling, by the way, is what threw me off, and why I ended up on the inside. I knew I'd heard that word a few times; but so very little that I had to look it up. And the "definition" that I found made me conclude it had to be on the inside. Not a native English speaker, nor a car expert!

Thanks for your patience and sharing your knowledge, on a Sunday, no less. I know what I'll be doing on Memorial Day :)
 
#24 ·
I'm back. Memorial day had other plans for my wife and myself; I spent 300 miles on the road with her for all kinds of doctor visits.

I got back under the hood today and before I could even turn on my VOM I noticed exposed/frayed wires on the back of the male connector to the OSS, on the wiring harness side. It's not the sharpest image, sorry; it's easier to see with the naked eye. I didn't notice that a few days ago; perhaps today the light just hit it at the right angle.

I suppose that happened after I removed the cable the first time, or even during installation of the new OSS. And that would explain why I now get a zero reading on the old OSS as well. Either way, if it was that easy for me to break it then it is high time to replace it.

I spent the afternoon looking in local bone yards. Found 7 Taurusses total; not one with the connector I'm looking for! Autozone guy told me they don't have it, same at O'Reilly; but Advance sells it, part number PT5962. Unfortunately no Advance store in a hundred mile radius has it in-store.

And now that I'm home I found it for 10 bucks cheaper at RockAuto: More Information for STANDARD MOTOR PRODUCTS S1085 . Their shipping is slower and costs more though!

BTW: the same thing is for sale on eBay, for $55, listed as an ABS speed sensor connector.

We'll be on a long trip North this weekend, and back. There's about 10 Advance stores in San Antonio, maybe one of those has these connectors in stock. If not, I'll have to order it. Ah, the joys of living in the middle of nowhere...
 

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#25 ·
I'm back. Memorial day had other plans for my wife and myself; I spent 300 miles on the road with her for all kinds of doctor visits.

I got back under the hood today and before I could even turn on my VOM I noticed exposed/frayed wires on the back of the male connector to the OSS, on the wiring harness side. It's not the sharpest image, sorry; it's easier to see with the naked eye. I didn't notice that a few days ago; perhaps today the light just hit it at the right angle.

I suppose that happened after I removed the cable the first time, or even during installation of the new OSS. And that would explain why I now get a zero reading on the old OSS as well. Either way, if it was that easy for me to break it then it is high time to replace it.

I spent the afternoon looking in local bone yards. Found 7 Taurusses total; not one with the connector I'm looking for! Autozone guy told me they don't have it, same at O'Reilly; but Advance sells it, part number PT5962. Unfortunately no Advance store in a hundred mile radius has it in-store.

And now that I'm home I found it for 10 bucks cheaper at RockAuto: More Information for STANDARD MOTOR PRODUCTS S1085 . Their shipping is slower and costs more though!

BTW: the same thing is for sale on eBay, for $55, listed as an ABS speed sensor connector.

We'll be on a long trip North this weekend, and back. There's about 10 Advance stores in San Antonio, maybe one of those has these connectors in stock. If not, I'll have to order it. Ah, the joys of living in the middle of nowhere...
Yep, that would definitely explain the zero reading, lol. For future reference, if you go to a boneyard, any 2004-2007 Taurus with the Vulcan 3.0 OHV engine will have the correct connector. If you manage to locate a brand new one, splice it in, and make sure the splice is wrapped tight in heatshrink/electrical tape. Leave the original sensor in and see if the problem is resolved :)

Btw, I doubt you caused that by messing with it. It was most likely rodent damage. What likely did happen, was when you replaced the sensor, you moved it enough to where whatever minimal connection it still had got broken.
 
#26 ·
Rodents, huh? I believe you! About 5 years ago we called the satellite TV company after we completely lost satellite reception. Guy checked everything, and everything was good, except for the coax cables! Totally chewed in half by some kind of rodent. They, and goats, don't seem to mind copper wires...

Anyway. I don't need the Bull until next week, on Friday. Even if I have to order that connector to my home, or the "nearest" store, it'll be here on time. I'll give the "old gall" a break for a few days.

Thanks for your generous help and free support!
 
#27 ·
No problem, let me know if the problem is resolved when you get to it (or not ;)). And yeah, rodents are really annoying. I had one chew up one of my ignition wires for the EMI capacitor. They just love stealing the insulation for their nefarious purposes.
 
#28 ·
Oh and as far as today's visit to the bone yards is concerned: each and every Taurus had their engine/transmission removed. Some still had (parts of) the wiring harness; but not one of them had the proper connector - that I could see. And in case of half of them I always got this "hmmm, this looks different" feeling, every time I looked inside the engine compartment. So those Taurusses may have been from before 2004.

And I'll follow your advice and leave the old OSS in there, after getting the new connector. If things go the way (I think) you suspect then that will be another hair pulling experience, lol!

Learning something new every day is fun.
 
#29 ·
I'm working on this again. UPS delivered the connector yesterday; but I didn't have time to work on it until this afternoon.

I was able to pull that end of the harness up to a point where it will be easy enough to put the new connector on. I had to disconnector another connector further down, for which I had to remove the driver side wheel. And use a hammer and a dowel to knock out a plastic pin. All good fun.

Now that I have it where I can clearly see the wires it really doesn't look that bad. Yes, the copper is exposed; but both of them still seem connected. I tested the ground (red) side of it; and it toned good right away. Regardless, the connector will be replaced, in case they got shorted (and I imagine that would be easy, with just a bit of rain/humidity, or might happen in the future).

I also took your advise and unplugged the PCM connector. That in itself was a marvelous adventure! What I noticed right away is some light signs of fluid. Really small drops of ... something. I wiped it off and it can't be seen anymore in the photo I took.

The reason I took the photo was to ask how the pins are numbered. I couldn't see anywhere on the connector that tells where pin 1 is, nor any other numbers. But some Googling later I found a diagram of a Focus, which seems to use the same connector. Pin 1 on the top left, pin 79 on the bottom left. So 84 and 91 I can find.

Correct me if I'm wrong, please!

Also, another trip to Autozone is in order. Getting those 5.5 mm screws out was not easy! I used a small set of locking pliers; but I won't be able to put those screws back - securely - with those same pliers. Perhaps I can get reimbursed for that, with father's day and all, lol!

Will keep you posted. I'm on a break. It's close to 100 F out there...

Oh, and: I guess I located the cabin air filter, by removing that cowling? That thing is old and needs to be replaced. Is there just one of those?
 

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#32 ·
Thanks for that confirmation, Sheila. I shopped around before leaving the house, and found them at Autozone; but much cheaper at Walmart. A 500 ft, $5 difference. From the Fram folks - with baking soda c/o Arm N Hammer, lol. Oh, it's gonna smell so fresh!! Baking soda in our ride, who would've thunketh...

Also got the 5.5 mm / 7/32" socket to put the bottom of the cowling back in place. Cheap set at Walmart, less than $10. Unfortunately, by the time I got back home it was dark; so the Bull will have to wait another day.
 
#33 · (Edited)
The bull rides again!

I'm good to go. I spent several hours on this brutally hot and humid day, checking everything carefully. Much to my dismay the wiring harness checked out just fine.

But I did install the new connector anyway, as I had planned. And cleaned all the grounds that I could find. It took me until close to sundown (and two changes of T-shirts) to go on a test drive; but it worked right away! And I put the new speed sensor in there. Hey, I paid for it, might as well use it, right? :lol2:

And the new cabin air filter doesn't look bad either! :D

Thanks to everyone for your advice and support. Y'all are amazing! :redirect_logo:

(another sideways pic - sorry!)
 

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#34 ·
Congrats! And yes, it was a hot one even up here. The thermometer crested 95 degrees. I stayed inside...lol

Sounds like the exposed wiring was shorting out somehow and that was it. Enjoy more happy motoring and feel free to open a new thread if something else pops up :)
 
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