Hello all. I own a 94 B3000 3.0 4x4 with 219k miles. It runs great, but I finally got sick of looking at the speedometer needle bouncing all around, so I replaced the speed sensor with a new one from Autozone. My first test drive was successful - it seemed to work normally, but then the ABS light came on. I remember replacing the ABS light some years ago by the rear diff and haven't seen it light up since. I thought maybe something there was something funky going on with the electrical, so I replaced the ABS sensor again. But, I started the engine and ABS light still came on.

I started inspecting the new speed sensor and there looks like there was a little oil dripping out of it. I don't know if that was related to the holding pin getting a little bent while trying to pull it out of the old sensor or what but there is some play in it. I'm able to push it in and out a little (not sure if this is normal). The new sensor didn't come with a new pin, which would have been handy.

I pulled the electrical connector and there seemed to be a little oil in there too. Of course - not sure if that's what's causing the issue. The new Duralast sensor had a little crown-looking plastic guard that I needed to remove so that the cable could be inserted into the sensor. I assume that was a dust cover or something, but I remember seeing a little gasket that came off with the plastic guard that I'm now wondering if was supposed to remain in the sensor somehow. I plugged the electrical connector into the old sensor temporarily to see if the light went off when the truck was on, but it made no difference. Of course, in the process of taking it on and off a few times, the fasteners snapped, so I now have a new electrical connector on order.

Did this sensor just get flooded with oil or something that caused the ABS light to come on, or do you think there something else going on? Thanks in advance.

 

Welcome to the forum

1994 Ranger/Mazda used a speedometer cable
1995 and up used electric speedometers and a VSS thru 1997

Both would have this unit on the transfer case(4x4) near rear output shaft: https://www.therangerstation.com/tec...s_withgear.JPG
New one without the added gear seen here: https://www.therangerstation.com/tec...peedsensor.gif
Gear is changeable to calibrate speedometer for tire size and axle ratios
These units had the speedometer cable hook up thru 1997

The 2 wire VSS on this unit was only used for Cruise control in 1994, and then for electric speedometer and cruise 1995-1997
But no connection to ABS

Rear axle ABS sensor has no connection to speedometer until 1998 to 2000

So we may be talking about different things here
Check your date on on the driver's door label, back edge
It will have the Date the truck was built, 7/94, July 1994 is a 1995 model year, so anything build after July is 1995
If built in 6/94 or earlier then it is a 1994

An ABS unit Resets with each Key off and then Key on
ABS light should come on with key on as a Bulb Test, and then go off
If there is a problem with an ABS sensor the ABS light will not come on until you are moving and it detects a problem

If ABS light stays on after bulb test then there is a problem with the wiring or the ABS unit

 

thanks for the help. Mine was built in 8/94 so I guess it’s a 1995 for purposes of this problem.

in the second picture you posted, you’ll notice that white crown looking thing in the sensor. Do you know what that is? The original sensor didn’t have that, but the new duralast replacement did. I could not insert the speed cable with that in place, so I pulled it out with needle nose pliers. Maybe that’s where I went wrong and that was a sign that it actually wasn’t the right part?

All I can tell you is that the abs sensor never came on in years but suddenly did within the first several miles while driving after replacing the speed sensor and has been on ever since. I didn’t touch the abs sensor until tonight when I swapped it out and saw that the abs light still came on steady after the ignition on bulb test. I then swapped it back to the existing abs sensor (which as I said had been replaced years ago successfully and fixed the last abs light issue) and the abs light still came on (no surprise).

Do you think I should put the new abs sensor back in and drive around a bit to see if the light goes off? Is there really no way that the abs sensor is related to the speed sensor? Seems like it’s a crazy coincidence that the abs sensor or abs unit would suddenly go bad after replacing the speed sensor.

 

The "white crown" is where a speedometer cable would connect, on a 1994, shouldn't need to remove it, never have myself so not sure what the results would be
It would just be left as is on a 1995-1997, unconnected

The 2 wire plug-in is the VSS(vehicle speed sensor) it is a VR(variable reluctance) sensor so it generates its own AC voltage as the gear spins the shaft inside when vehicle is in motion

100% for sure there is no electrical connection between VSS system and the ABS system until 1998
Only "connection" would be with the wiring under the truck
The 2 wires for ABS sensor run along drivers side frame rail and join with the VSS wires in the harness going into the cab, wires don't connect, just near each other
The ABS valve is in the drivers side frame rail just where it bends up to engine bay, 3 or 4 wire connector there

 

Are you saying that the VSS and ABS only join into a harness going into the cab on 1998+ models or even on my 1994/1995? It sounds like it's too far away from both sensors that it to possibly have come loose in the process of replacing the VSS anyway.

​​​​​​Removing the crown on the Duralast VSS was the only option as it not only blocks the holes for putting the fastener clip through, but it blocks the speed cable from inserting all the way through the sensor to engage the gear. As I mentioned, the old sensor didn't have that white crown. It just seemed really unusual that the crown would be put there as some sort of dust cap that you're supposed to remove. I just ordered another sensor on Amazon that doesn't look like it has the crown by the pictures, so maybe I got the wrong VSS sensor.

These things shouldn't drip even a little oil if properly installed, right? It's just really perplexing that even when I plugged the 2 wire VSS connector back into the old sensor just dangling there as a quick test the ABS light still lit up solid. The VSS harness looked like it had some oil in the contacts, so maybe it's fouled? I'm reaching here. I have to replace it anyway since the clips broke off while removing it a second time.

Do you think I should try the new VSS with the replacement harness and/or leave the new ABS sensor in? This one has really has me puzzled.

 

So you have a speedometer cable?
Yes or no?

If yes, then remove the white crown to install the cable
And you do have 1994 setup and wiring, even if an 8/94 build date, maybe a Mazda B-series thing

The VSS was dropped in 1998, so the hole was no longer there in transfer case to install it
The rear axle ABS sensor wires run to the ABS module inside the cab
The VSS wires run into the cab
But no connection between them, until 1998 to 2000

 

Yes, I have a speedometer cable. I don't have cruise control, so the 2 wire VSS is for what then, just cosmetic? Do you think I should be concerned if there's any oil leaking out of the speed cable on the VSS, even if it's just a little? I don't think there was any on the old speed sensor.

​​​What do you think I should do then? Put the new ABS sensor back in and hope that it was just a fluke that the old one failed at the same exact time I replaced the speed sensor? Now that I think about it - and memory on this is a little hazy, but I believe the last time the ABS sensor was replaced I don't think it immediately cleared the abs light. I remember having a mechanic do some other work for me and asked him to install the new sensor while he was in there and being disappointed that it didn't fix the problem. But then it eventually went away. I think. 🤔

 

I went out to the truck and fired it up. First try, no ABS light. Second try, it stayed on. Third try, it went off again.

I guess I should have mentioned that I do occasionally have one persistent electrical gremlin. It only affects the left turn signal arrow on the console and not the actual blinker. It always happens after I do anything unusual like disconnect/reconnect the battery or like when I replaced the radio a couple of weeks ago. The problem always goes away usually after the second or third drive. However, the ABS light hasn't been an issue in years. Do you think there might be a loose or corroded wire somewhere that could explain it?

 

Update on this:

I installed the Dorman speed sensor from Amazon - the one that didn't come with the white crown but said it wasn't supported by my model vehicle. It had a gasket already installed in there whereas the Duralast gasket was attached to the base of the crown. The original sensor was so old and fouled that I couldn't tell if a gasket once existed in there. I may have been able to pull the gasket off the Duralast crown and fit it into the sensor like the Dorman, but at this point I figured I'd just stick with the Dorman. The speed cable seemed to fit further into the Dorman than the Duralast (though maybe that was just luck) and didn't have any play when I tugged on it, unlike the Duralast. I also replaced the 2 wire connector whose tabs were snapped off and connection contacts were also coated in oil from the leaky Duralast sensor.

Fired up the truck, no persistent ABS light. Took it on a few mile drive to Autozone to return the VSS and ABS sensors and everything is perfect. Took a quick look at the outside of the sensor and didn't see any oil leaks, so I think I'm good. Thanks for the help.