Resistance rear wheel speed sensors

[J_C]

I have conflicting information about which pin #s on the pictured connector. On the wiring diagram I posted previously, it would have been pins #1 and 16 for the rear sensor, but on this diagram it is pins 21 and 22.

I would check both of these combinations, but ultimately if you want to know for certain you would look at the colors of the wires at the rear sensor, on the connector it plugs into, then either use insulation displacement meter probe tips to pierce that color wire at the ABS module connector, OR using an extension to the multimeter leads, test for resistance between each contact of the ABS sensor connector's two pins, and each contact in the ABS module connector.

Yes you should be able to use the OBD2 dongle and Forscan to see the ABS speed sensor data in realtime. I don't recall what the menu choices were but it should be obvious when you have the right one.

 

[FrankT99]

Thank you for all the help!
For both BAFX scanners it says:
'This OBD2 scanner does not read ABS, SRS, TPMS or Oil Change lights;'.
I think also the Torque Pro doesn't support ABS but the FORScan does support ABS
I switch the app?
Thank you for all the help!

 

[J_C]

Can you elaborate? Where do you see "does not read ABS"?

Forscan app should work with the BAFX dongle to read the ABS sensors, unless they or Forscan changed something.

 

[FrankT99]

For both BAFX in the Amazon page:

Amazon.com: Bafx Products - For Android Only - Wireless Bluetooth Obd2 Scanner Diagnostic Code Reader & Scan Tool - Scan, Reset & Clear Car Check Engine Light: Automotive

Buy Bafx Products - For Android Only - Wireless Bluetooth Obd2 Scanner Diagnostic Code Reader & Scan Tool - Scan, Reset & Clear Car Check Engine Light: Code Readers & Scan Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Under 'About this item'.

 

[J_C]

Look in the Forscan menus for the speed sensors.

 

[FrankT99]

FORScan Lite:

FORScan Lite - Apps on Google Play

Computer diagnostic of Ford, Mazda, Lincoln and Mercury vehicles

play.google.com

That's the one?

 

[J_C]

Yes, though I thought the free demo version was capable of it too. Wheel speed sensors might be abbreviated as WSS.

 

[FrankT99]

J_C,
I really don't want to bother you and thank you for all your help (I learned a lot...and you know a lot
I prefer not to download whatever version:
On Google Play I can find only the paid version.
And here? Which is the free version for Android?
FORScan Lite for Android: Download FORScan - FORScan Demo for Android. That's the one?
Thank you very much?

 

[J_C]

Yes, what you linked is the free "demo" version. It will only show one wheel speed sensor (called a PID on the comparison chart linked below) at a time (whichever you pick to display so can check all 3, just needs to have each selected separately), not all 3 simultaneously like the Lite, paid version on Google Play.

Elsewhere on Forscan's site is a comparison of other things the demo version cannot do, one of them being clearing codes.

Comparison of FORScan applications

Remember that the Windows PC/tablet version is also free and can do everything and more than the paid-Lite or the free-Demo versions, but it seems like a hassle to me to have a laptop or tablet while doing driving tests. A phone, you can just get a phone mount and have it visible while driving, with less distraction.

 

[J_C]

Don't know why I didn't think of this before, but as far as I know (you might want to research this), the rear differential speed sensor started being used as the main vehicle speed sensor a few years prior, on '98 and newer. If that is still the case on your '03 then if your dash instrument cluster speedometer is working correctly, so is your rear diff speed sensor.

 

[FrankT99]

Also ForScan shows that it is the Rear Speed Sensor (see image).

Next step:
The other images I attached show the disconnected connector to the ABS sensor.
It also shows that the connector/wire was repaired before.
It is a red and a green/black cable.
Question: Is there a left side and a right side for the wires to the connector (to the ABS sensor)?

 

[J_C]

There is no polarity, it produces an AC voltage signal so either wire can go to either sensor contact.

Since it has been repaired like that previously, you could cut the crimp off, and either re-crimp with a quality sealing crimp, or solder and heatshrink tubing over the solder joint, or measure resistance between the connector contacts and the ABS module connectors' corresponding contacts - But personally, I would redo it with a solder joint just so I know it is done well, to rule it out and make sure it is sealed from the environment and going to last long term, but I am pretty good at soldering. Some people are better at crimping.

-OR- you could first take the sensor off, examining for sludge buildup on it and washing it off, measuring resistance. If it is cracked it will need replaced. It might be fine but crack trying to remove it, so you could measure resistance again with it installed. Your decision which to try first.

The most comprehensive fix would be to both redo the wire connection and get a new sensor, but odds are both didn't fail simultaneously, is going to be one or the other (or some wiring fault further up or the ABS module itself... just going from most to least likely at this point).

Also examine the sensor contacts for corrosion. If the prior connector leaked and only the connector pigtail and not the sensor was replaced, it could have contact corrosion still and be back to where it was the last time the repair was needed.

This is much harder to speculate and write about than being there... visual clues are easier to see in person, like, maybe that crimp is good and sealed well, or maybe not.

 

[FrankT99]

Thank you very much!!
I cut the wires and then I connected the connector (repair part with white wires) with the old ABS sensor (the new one is installed in the truck). With the multimeter I got 1945 OHMS. That means that the old ABS sensor and the connetor with the white wires are OK. Correct??
If this is correct the problem could be the contact between the white and red/green-black wires or up the red/green-black wires in direction to the ABS module. What do you think?
Thank you very much!!

 

[FrankT99]

J_C,
The ABS light is OFF!!
It was the connection between the wires that failed (white to red/green-black). I connected it under the truck with crocodile clamps and the old abs sensor.
Thank you for your time!! I learned a lot and saved money! Also to have this $26 scan tool with the laptop is great.
Thank you very much!

 

[J_C]

Glad you got it sorted out. Now consider that if the first thing you had done was crawl under the vehicle and spot those crimps, that would have been my first recommendation. Even so, gotta have a scan tool for older vehicles, will pay for itself many times over.

 

[FrankT99]

I connected the wires with 'Dorman - Conduct-Tite 16-14 Gauge Butt Waterproof Connector, 10 Pack, Blue' but it seems so that there is still a loose contact. It worked and light and code was gone but with some light bending of the butt connectors the light is back on. Welding is not an option for me. Isn't there something better to bring this wires together?
Thank you very much!!

 

[J_C]

I have not used that Dorman product so I don't know how good it is, but often the larger part of getting a good crimp joint is a good crimp tool. If you don't have one then I would try crimping it some more with pliers.

What do you mean by some light bending? Is the wire not secured by the plastic ends? They need heat shrunk after improving the crimp.

 

[FrankT99]

Hello J_C (and all the others),
I'm back.
Question:
With the motor running what Voltage should be at the connector of the harness of the wheel speed sensor?

 

[J_C]

I've never measured voltage with engine running. They are passive sensors so in theory they wouldn't need any voltage supplied, don't know if there's any stray voltage coming from the ABS module but if so would be DC and can be ignored. With wheel spinning fast enough to register, they should produce low AC voltage.

My factory sensor fell apart when I removed it, no active components just the electromagnetic wire wrapped coil, so I'm 100% certain they're passive.

Home | Apec Automotive

apecbraking.co.uk

 

[FrankT99]

Hello J_C,
I'm happy to hear from you!!
I checked the voltage of the harness connector once again and it is on one side a positive voltage and on the other side a negative voltage. Could be the reason that I switched the wires to the connector?