Can somebody explain wheel speed sensors to me

hey

I have a freightliner which keeps coming up with a wheel speed sensor on the 1st axle RH side.

I got the mechanic to replace sensor and cable, but now it keeps coming up in weird ways.

I can drive 5000 miles and it won't come up, but then if I drive bobtail it will trigger more often. It will be stuck on for a day, and then the next 5 days nothing.

How do I measure the ohms to check each sensor?

where do the sensor cables plug in? do the go to a valve somewhere or go to a computer?

could the cables be swapped at the valve/computer meaning the wrong location is showing on the dash?

I am home for a few days soon, so would like to spend some time on it to get it sorted

thanks

 

Not sure what sort of faults you're seeing but I wonder if it could be caused by a loose wheel bearing or an issue with the tone ring on the hub?

 

sorry forgot to mention I went through a suspension place the other day and got them to check that wheel for movement and they said all was good

 

Follow the wire from the wheel end toward the frame and you should locate a connector at the wiring harness. Anything over 2K ohms is considered to be bad.

 

Also check the wire connections from inside wheel end to computer.
I have 2 pieces for each cable from wheel end to computer. Those connections can get loose and corrode.

 

so the cables go to the computer? I am assuming you could mix up the plugs at the computer so it would show the wrong wheel faulty?

 

You can’t, sorry it is a sensor that has electronics in it and it is tested by an ac volt meter and spinning the wheel.

this is a wiring harness problem most of the time, not a sensor issue.

 

Start by finding a schematic for the truck wiring. Unplug the sensor and check continuity between the harness plug and the pin out at the abs unit under the dash. Ohm meter, long leads with alligator clips. The twisted pair may have chaffed bare and shorting or the wire may be broken inside the insulation. Copper wire gets brittle with all the vibrations over the years. I have a million mile truck and am chasing broken wires all the time

 

ECU is usually located on frame cross member, under or at the front of fifth wheel. I would first make sure the new sensor isn’t getting loose and away from the tone ring. Push in on it from the back, using a stick, Long 1/4” extension works good. If good I’d swap the extension wire between sensor and ecu. Unless the new sensor has just 1 long wire straight to ecu. I’d swap the extension wire if equipped. I would also check the ride height. If it’s too high, might be getting wheel spin, especially while BT. Might be aggravated by bad shocks.

 

With all due respects, why do you say, “you can’t”? What are you suggesting the sensor is designed and made of that cannot be checked with a 10 megaohm multimeter?