ABS / brake warning light - bad speed sensor

I have a 2008 Tacoma with a code saying one of the rear wheel speed sensors is bad.

my mechanic has replaced it twice and it is not fixing the issue. What should we look at next? Pigtail wiring?

I first noticed the lights coming on while driving on the highway, they went back off within about a minute and then started coming on more frequently here and there during the same Drive. I did notice the ABS started to act a little funny and occasionally after I would put it in park it was almost as if one of the brakes was a little locked up just for a second when I started to drive again. Fluid is good. Help!

 

What code(s) are you getting ?
If it's a circuit fault code you need to check circuit integrity from the sensor to the ABS module.

 

^What's the actual fault code? If it's a circuit code, then more likely to be wiring.

You can monitor the wheel speed sensor output in real time with a OBD2 dongle and an app like Torque Pro. If the data looks OK but has a periodic dropout, then there's might be a dead spot on the tone ring on the wheel bearing. Rear wheel bearing replacement is a big job.

 

He mentioned the tone ring to me today, he was trying to see if it had any problems but said it’s a little hard to observe and look at.
I’ll confirm code and post it

 

^A scanner or OBD2 dongle can have the four individual wheel speeds displayed in real time. This is "processed" data from the ECU so it shouldn't be noisy. Drive along at a constant speed and the wheel speeds should be flatlined. If one of the four has periodic dropout, then the tone ring is suspect.

 

Co215 is the code

 

It could be just the harness (connector or wiring). Before replacing the sensor, did the mechanic check for output of the sensor/continuity of the harness? On my wife's 2010 Prius, it was the sensor AND harness once (one pin corroded which caused a corrosion break on both the connector in the harness and sensor), and only the harness another time (other side). Luckily, I had a Waekon ABS tester so it was pretty easy to narrow down (it can check for sensor output as well as send a signal up the wiring to see if the module is receiving signal).

 

Replaced wires, still have both lights on.

I was looking at the part which the tone ring is part of, is that the potential next thing to check?

truck drives and brakes fine, is it safe to drive?
Dealership appt Monday

 

The tone ring is part of the wheel bearing (part of the rear seal of the bearing). If you already replaced both the sensor and the harness, then it could be the tone ring of the bearing.

You can't replace just the tone ring - you have to replace the bearing assembly. Worst case scenario is the brake controller itself but that's pretty rare (and $$$).

You already have an appointment, so it's moot, but I was going to say if you live in/near NH, you could use my Waekon to check.

 

I drove with a bad speed sensor and the abs/brake light on for a year. You won’t have ABS so you can pretend like it’s and old truck where you work the brakes when it starts to slide on the snow.

 

Forgot to mention - it's "safe" to drive as far as the brakes will still work as usual - just no ABS and if you have any type of traction control, those get disabled as well (because they depend on the system being able to read comparative wheel speed.

As @91859 stated, you will essentially have 'normal,' non-abs brakes.

Also, if you live in a state with safety inspection, it will usually not pass - but that doesn't mean it's inherently not safe, just no abs action (if a situation calls for it).

 

Appreciate y’all so much! I will see what the dealer says Monday. It feels completely fine when I drive it so I’m not gonna stress it too much