ABS Light On / Replaced Wheel Speed Sensor + Wheel Bearings

I have a 2007 Tacoma with 220,000 miles on it. About a month ago the ABS light came on. We pulled the codes and it showed a Left Front speed sensor. I ordered a replacement and put it in. The light stays on. We noticed grease on the end of the sensor and found a couple of posts about wheel bearings causing ABS failure due to excessive grease inside the hub. We replaced both front wheel bearings with the Dorman bearing/hub assembly and reset the ABS. Everything looked good but the light came back on, still throwing the left/front speed sensor code. I swapped the left/rear and left/front speed sensors and the light stayed off during a test drive. Now the light is back on and throwing the left/front speed sensor code with a message about debris on the sensor. There is some grease on the tip of the speed sensor. I cleaned the hub very well and did not apply any additional grease inside the hub, so I can only assume the new bearing lost some grease already. I checked all of the left/front Speed Sensor harness and couldn't find any damage/shorts in the segment. Has anybody run into anything like this? Seems like a pretty simple system...
Thanks!

 

Based on my experience, I don't think the grease would cause the problem. I changed both of my front wheel bearings in the last 4 or 5 months and I put some extra grease in the cavity and even put some on the speed sensor to keep it from seizing, for future removal. I don't have any problems.
I'm just spit balling here, but I'd trace the wires back to wherever they plug in away from the hub and see if there's any damage to any of the insulation.

 

You could check the sensor circuit on the harness side for voltage.
Don’t be afraid to move, pull, and tug on the wire harness. This will help check for an open in the wiring.

Other than that, you’d need to check the sensor output.
A scan tool capable of monitoring active data on the wheel sensor would help.

 

Thanks! Had a solid 10v and shook the harness a along it's length. I figured taking the known good sensor from the rear would rule out the aftermarket sensor as the culprit. I'm thinking there is some issue in the harness.

 

Yeah, the voltage check is only good on one side of the circuit.
You still have the “negative” side back to the Skid Control module (ABS Module).
I don’t know what you’d be looking for on that side. @Dm93 probably knows.

I’d maybe check the wiring integrity to the ABS Module.
But first, I would make sure you have good pin contact at the connector.
Maybe you have a bad pin or loose contact?

 

I suspected loose/bent contacts as well so made sure to clean and adjust the contacts to make sure the connection was secure. There was some corrosion on the plug side that I was able to clean up.

 

And the problem is still there?

 

I had done all of this troubleshooting yesterday. Still scratching my head on the problem.

 

If you are down for checking the wiring to the ABS module then check your PMs.
Other wise, I can’t think of anything else.

 

Will your scanner read/graph ABS data so you can see what the sensors are doing while you are driving?
If the wiring checks out it could be an airgap/tone wheel issue, grease on the sensor shouldn't affect it as long as there is no metal contamination in it.

I'd want to look at the speed sensor PIDs while driving and see if there's glitches or dropouts and if so when they occur.

 

It ended up being the speed sensor harness. Couldn't identify exactly where the wiring issue was but spliced in two new wires between the wheel speed sensor and the connector in the engine compartment and the ABS light went out. New harness ordered which was another pain in the rear...