False ABS activation?

Hey guys i'm just looking for some suggestions here. My 2004 Tundra began having some weird ABS related issues about a year ago. Right as I was about to come to a stop my ABS would activate(the pedal would actuate) and I could not figure out why. I took it to Toyota and they said that it was the ABS actuator(1700 dollar part) that was the problem. Important to note that hey also said it's not my wheel speed sensors and that they are working correctly. I decided to go get an actuator off of the my same truck but from a salvage yard and installed it. It also did not fix the issue. So I'm pretty stumped and I do not want to take it back to Toyota to further diagnose since they are really expensive. Any suggestions? I've had people say its my tires since they are slightly bigger than stock but that didn't seem be an issue initially. Any help would be appreciated.

 

I've fixed this exact issue on my friends 2006 tundra. The ABS activated from about 5 mph and under with no wheel slippage. The issue was iron filings built up on the magnetic tip of a couple of the ABS wheel speed sensors. If you can monitor live ABS data, you can drive at 2 or three MPH and see which sensors aren't reading wheel speed, or you can just pull them and clean them off.

Of course, those iron filings came from somewhere, and that somewhere = wheel bearing(s). So unless you've just done a wheel bearing, you'll probably need at least one.

 

I would have assumed that Toyota would have done that to begin with. I do not have a way to monitor the wheel speed sensors however, I was very clear with Toyota and they said they were operating normally although my front two sensors are dropping off slightly before the rears. Did your friends Tundra have larger than stock tires as well? Aside from a shake test how would I know which bearing to replace assuming the sensors are not covered with metal filings?

 

Stock size tires on his truck. Do make sure all 4 tires are the same size and correctly inflated, if you haven't already.

If your front sensor readings were dropping off before the rears, I'd pull them first and check for filings. They should all read at 1 mph / 1 kph. Pretty sure I pulled and cleaned all 4 of his, as long as they aren't stuck in the bore and the bolt isn't seized it's an easy thing to do.

If you don't have filings on the sensor, and no howl at highway speeds, and no play in a wheel bearing then you needn't worry. If you find a bunch of iron on a sensor, then you'll know.

 

Ok, I'll go ahead and check that out later today. What was your method of cleaning. I've seen several different ways.

 

And yes, you'd expect any dealer tech would be able to handle this easily. Unfortunately, 10 years of working in various ones (not automotive) I know differently.

 

Wiped with a cloth, might have used an air nozzle to blow the last of the sensor tip clean. A bit wheel bearing or other grease helps the sensor o-ring slide back into place without rolling / cutting.

Keep us posted.

 

Alright, I will go ahead and give that a shot and I'll let you know how it goes. Thanks for the advice!

 

Take some pics and post up how it goes!

 

Alright so I check it out and it didn't too dirty. At least the metal part on the sensor didn't seem dirty. Maybe it was really dirty and I'm just not sure what I was looking at. The first two are the left side and the right two are the right side. Let me know what you guys think.

 

Compared to one guy who posted up pics a few months ago yours looks good. I see a few specks of debris inside but see no shavings. Good!

The sensor pics look blurry so its hard to see if there are shavings on them?

 

Those look pretty damn good. Looks like there might be a tiny bit on the second one. Make sure the sensors seat all the way in the bore and aren’t held out by rust scale or anything. Proper gap to the tone ring is critical.

 

There wasn't anything on them really. So safe to rule that issue out. I did notice when I drove up and down my hill that my speedometer took a full second or second and a half to register my speed. Is that a sign of a weak signal?

 

Not sure about the speedo question. Might as well pull and inspect the rears as well. It’s cheap and easy.

 

I'll revisit this tomorrow. Thanks for the suggestions again.

 

Quick Update. I swapped stock wheels and tires onto the truck to make sure it wasn't my tires causing the problem and the problem persist so that was good. At least its still a consistent problem. After I had swapped my wheels back on I decided to see what would happen if I unplugged the wheel speed sensors. As expected the problem went away. The plastic connects were covered in crap so I got an electrical plasitc clear spray I think it was called qd cleaner and spayed them down. Reconnected the connector and now the ABS light will not turn off. Most likely damaged an electrical component while I was messing with it.

I'm still thoroughly stumped with this problem. All signs point to an electrical issue not a mechanical issue.

Heres what I know:
Its not tires
Its not the ABS actuator
Its not wheel speed sensors(according to Toyota but I don't really believe them)
-The rear wheel speed sensors are good
There is no air in the system since I recently bleed the system.

What am I missing?

 

It will take a drive or two to get the ABS light to go out after the truck was driven with the sensors disconnected.

From here you’re pretty much going to need to be able to monitor live wheel speed data from the sensors to get any further. If you have an old laptop, you can buy the cable and Techsteam software for less than another trip back to your dealer.

 

Check your rear brakes. I didnt have mine adjusted right and it caused the exact same issue.

 

Update: I took the truck back into the mechanic's shop that I originally took it in for and had them run a test on my wheel speed sensor. They say that the new ABS Actuator I had installed was actually bad and that it was short circuiting. I have another on the way, also a used part, but it was free so I figure it'll try it out. The rear sensor will be checked when I go to install the other ABS Actuator. Sorry I haven't been active on this the last week or so I got a lot going on. I will let you guys know what comes from that parts. If its still not working I think I'll just accept I don't have ABS.

 

Final update:
I decided to bite the bullet and buy new front wheel speed sensors. Turns out that was the problem the entire time although I had a mechanic shop and the TOYOTA DEALERSHIP tell me it wasn't the wheel speed sensors. I am beyond pissed but its done and fixed. Thank again for everyone's input on the forum it helped me out a lot.

 

Thanks for updating us. I'm actually dealing with this exact issue. I just ordered a replacement sensor this morning so I'm hoping it solves my problem like it did for you.

 

Brand new OEM front wheel speed sensors fixed the problem! Not ABS sensor even though ABS was activating below 5mph during braking.

 

Unless I'm mistaken, ABS sensor and wheel speed sensor are the same thing. Different names for the same part.

 

You are correct.

 

@FirstGenVol do you know what ABS kit you went with? I picked up a replacement set off Amazon and the fitment is all wrong.

 

You talking about the wheel speed sensor? I got one off Amazon as well and it
It didn't fix my problem though.

GRQV-1007282248

https://www.amazon.com/dp/B076DNHYDB/ref=cm_sw_r_cp_apa_i_CVLoDb4T9VRXR

 

Yep, thanks. I'm working on an 06 double cab, the connection fitting is different from what you are showing. Trying to avoid ordering the wrong part again.

 

Sorry to resurrect a dead thread. This came up on my search for random ABS activation. I found the issue for mine. The larger tires I have clipped the Speed Sensor wire and would cause a short. It only happened in hard right turns, so it wasn't to hard to narrow it down.

 

Is there a different bracket we can install during hard right turns?? Each time the front wheels come off my truck the sensor goes out.

 

I am having the same issue at low speeds after the rear bearings were replaced. Shop bled the system three times and the diagnostic tool didn't throw any codes. Took it to the dealer, bled the system and no codes. I still have the issue during low speed stops. What do you mean by adjust the rear brakes? Star adjuster? more rubbing or less? Thanks in advance.