Anybody ever damage an ABS speed sensor? (1 Viewer)

[okryan]

99 LX. I replaced a bad CV axle over the weekend. All seemed to go fine (but I remember fighting with the brake caliper - never unhooked the brake lines). Drove the truck about 50 miles and seemed fine. Then ABS and brake lights came on, accompanied by the continuous beep. Brakes worked fine. After about 20 minutes of running time and controlled test drive, the lights and beep went off. Next time I started it, they returned and now there's no brakes. Pedal has no resistance down to near the floor, and then it will apply brakes if I push real hard. Bled the brakes - no change. Could be a master cylinder or brake booster, but I wonder if it could also be a damaged speed sensor (damaged during the CV replacement). No diagnostic codes show on my wal-mart code reader.
I appreciate any input.

 

[badlander]

Sounds like maybe the brake line got cracked from stress during the axle job and is leaking fluid. Any fluid present?
I don't believe the speed sensor would have anything to do with the pedal going to the floor.
Also, your code reader will most likely not read ABS codes. You have to access them manually via the port under the hood using a jumper wire and then read the blinking light sequence on the dash display.

 

[savirc]

I had the exact same lights come up ABS etc. After inspection surprised ABS sensor was chewed, due to an improperly installed inner axle after an accident (previous owner). There is not a whole lot of clearance between the sensor and the abs ring. Any fluctuation in the ring or sensor and it will get chewed then you have Christmas tree in your dash.

 

[okryan]

Thanks guys.

badlander - doesn't seem to be cracked or leaking brake fluid anywhere. Plenty of fluid in the reservoir too.

savirc - thanks for the input. I'm going to check the sensor before I tear into the brakes. Did your actual brakes stop working, and then the system worked again when you replaced the sensor?

I'll check the sensor and post an update. Gracias.

 

[savirc]

Thanks guys.

badlander - doesn't seem to be cracked or leaking brake fluid anywhere. Plenty of fluid in the reservoir too.

savirc - thanks for the input. I'm going to check the sensor before I tear into the brakes. Did your actual brakes stop working, and then the system worked again when you replaced the sensor?

I'll check the sensor and post an update. Gracias.

Inspecting the sensor will take 5 minutes, maybe 10 if you are in the rust belt... be gentle its plastic you can break it off if you are not gentle. If its stuck spray some WD-40 before attempting to pry it off.

If the ABS sensor malfunctions you may get what appears to be brake malfunction. The reason is your ABS, VSC and ATRACK (Yours doesn't have ATRACK Maybe not even VSC) have input in the behavior of the brake system

In my case because the sensor was not sending signal it activated the ATRACK which made the truck act like it was stuck activating brakes.

 

[PADDO]

As badlander says you want to pull codes (via dlc1 and shorting strap) if you don't have an ABS capable reader and see where that takes you. Captain Obvious says the loss of brake hydraulics in conjunction with lights and buzzer isn't good. Here's a brake dtc matrix, from an 04, that may give you an idea where to look. A chewed up speed sensor should throw its own code.

 

[okryan]

I pulled the driver's side speed sensor (the one in question). Sprayed with penetrating oil and let it sit for a day, it pried right out with a screwdriver. It looked fine except dirty. I cleaned it with MAF cleaner (seemed like a good idea at the time). Reinstalled, unhooked battery for 15 min to hopefully reset computer, and no luck. Still got lights and buzzer. Then I checked the resistance on the speed sensor, and it matched the resistance on the passenger side sensor (about 1 kohm), so I think the sensor is OK and there's probably a bigger problem. I'll try to figure out how to do the manual code reading thing.

Thanks!

 

[okryan]

Pulled the master cylinder. Took the motor apart and it looks worn, but maybe or maybe not worn out? Anybody have a source for a rebuild kit? I'm also going to rebuild the pump piston since its out, following Skidoo's post: Master Cylinder Rebuild - DIY

 

[Sandroad]

If that motor is as bad as it looks in the photos, it's shot.

 

[okryan]

Probably. I don't have much experience with them. My father in law has a starter shop so I'll probably see what he can do with it.

Sent from my XT1097

 

[okryan]

Update: Took the electric motor into a motor shop, they cleaned all the carbon dust out of it (it was bad) but didn't add any new parts. They tested and it was good. I also got the pump rebuild kit and installed according to : Master Cylinder Rebuild - DIY. No problems. Reinstalled master cylinder into the truck, filled with brake fluid and now the motor on the pump runs (it wasn't before). Still have the ABS and brake lights and buzzer. Brake pedal goes to the stop with no resistance at all. Do I need to bleed the brakes before the lights will reset and the pedal will work?
Thanks.

 

[Skidoo]

Rebuild of Master Cyl requires bleeding all brakes, takes longer to get air out of rear because of longer run.

 

[okryan]

Bled brakes. Rear drivers first, got some air out of it, then fluid ran clear. Rear passenger next, drained a lot of fluid (300+ mL) until it ran clear, no air bubbles. Front brakes will not bled any fluid, nothing comes out when the screw is opened. Either side. The pump motor runs when the key is turned on for about maybe 20 seconds. No warning lights with the key on, but when I start the truck I get the same ABS and brake lights with buzzer. Still no resistance to the pedal. Is there a possibility that the actual pump isn't working (I can hear the motor run), or am I missing something? I put the little star washer back in when I reassembled the motor to the pump, so I'm pretty sure the motor is actually connected to the pump drive shaft.
Thanks for all your help.

 

[uHu]

Double check mc rebuild?

 

[04UZJ100]

My ABS wire was ripped while doing work. We spliced it together and used heat shrink wrap. It's been fine for 10k miles.

 

[CanadianRockyCruiser]

I broke the mount on mine this weekend while doing the ball joints and axle seal. If you need to remove the ABS wire to gain access to the cv, consider doing it from the engine bay down, unfastening the clips near the upper control arm, and leaving it attached to the knuckle. My ABS sensors are rusted in tightly, so this is an easy way to make sure you don't damage the sensor by extracting it...as mentioned the plastic mount is easy to break. I'm lucky that mine still seems to work fine... for now...

 

[okryan]

Thanks all. I got it fixed. Rebled the front brakes and that was the problem. Not sure what I did wrong the first time bleeding them but its good to go now. I think it must have been the electric motor on the brake booster that was the problem.