wheel speed sensor

[mikkelstuff]

My 2002 4WD Ranger XLT check engine light tells me I have a front left wheel speed sensor not working. Is this a common problem? I have not crawled under to look at the thing.

I had the speed sensor remove last September when I upgraded to 2004 disk brakes but all worked until now.

 

[sgtsandman]

It isn't but it's common enough on most vehicles to recommend you look at the sensor to see if it has junk on it that needs cleaned off or that the tone ring needs cleaned before I would look at changing a sensor. The sensor is normally magnetic and could have pices of rust and what not stuck to it.

 

[Dirtman]

The wires get broken as well. They aren't very well protected.

 

[adsm08]

You probably have a bad bearing on the LF corner.

The air gap on that sensor is almost nothing, and it doesn't take much bearing play for the tone ring to eat the tip of the sensor.

 

[mikkelstuff]

Ok adsm08. So how do I know if I have a bad wheel bearing? This truck has never been off road but 140,000 miles add up.

'Course I had the wheel hubs off when I changed out the ball joints and brakes. I do see wheel hub assemblies are sold with the a new speed sensor included.

 

[Josh B]

Raise it up and wiggle the tire. When you pull the hubs do you have to readjust the bearings? Maybe didn't adjust them quite in enough

 

[mikkelstuff]

There is no adjustment on the wheel bearings when removing/installing the hubs.

 

[adsm08]

Ok adsm08. So how do I know if I have a bad wheel bearing? This truck has never been off road but 140,000 miles add up.

'Course I had the wheel hubs off when I changed out the ball joints and brakes. I do see wheel hub assemblies are sold with the a new speed sensor included.

Like Josh said, jack that wheel up and wiggle it. Bearings usually will show play top to bottom and side to side, but I just did one on a Explorer that only showed play top to bottom, so it can be helpful to have someone watching for what is moving.

Another helpful tip, if the bearing is causing the play applying the brakes will hold the bearing still and make the play stop.

When you pull the hubs do you have to readjust the bearings? Maybe didn't adjust them quite in enough

No, an 02 4x4 will have a sealed unit bearing that can't be adjusted. However having the axle nut too tight or too loose can damage the bearing and allow it to get sloppy. I've found too loose makes it happen faster than too tight, but there is quite a tolerance on either side of the actual torque spec.

 

[pjtoledo]

check the torque on the axle nut, that may buy you some time.
do you have a needle type multi meter? if yes open the connector at the frame and clip on to the 2 pins.
set to ohms check for continuity, then slowly rotate the wheel. if the sensor is good it will cause the needle to oscillate.
that's not a 100% test to check for a perfect sensor, but will reveal if it's dead.

 

[mikkelstuff]

Finally got a chance to jack up the Ranger. There is no slop in the wheel bearings that I can find and the speed sensor is still in place.

Strangely enough, the "check engine" light went out on its own. I think if I get another check on that speed sensor, I'll replace it.

Wrote too soon. Warning back on for speed sensor!

 

[mikkelstuff]

Replaced the left front wheel speed sensor today at the Ranger is happy again. I didn't even have to clear the error message.

I didn't see anything looking bad in the original speed sensor. I did check this sensor and it showed 403 ohms resistance across the contacts. I never thought to check the new sensor for comparison.

I did notice that the teeth inside the wheel hub were largely filled with a clean blue-green grease. Is that to be expected?

I wouldn't think this grease mattered unless I have a wheel bearing seal failure. I did clear the teeth before reassembly.

 

[adsm08]

The grease won't hurt anything. Probably best to leave it actually.

The wheel speed sensor creates it's signal by the magnetic teeth passing through the EM field created by the sensor. That makes electrical spikes on the circuit that the module can see and translate the frequency into a speed.

The grease, not being magnetic, has no effect on the signal generated.