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ABS Light On But Brakes Feel Fine Diagnosing Wheel Speed Sensors

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ABS Light On But Brakes Feel Fine Diagnosing Wheel Speed Sensors

Created on: 2021-01-07

Watch this video to see Andy's explanation and diagnosis of how an old rusty wheel hub can interfere and set off your ABS light!

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Here we have a 2010 Buick LaCrosse with an ABS light on. We're going to check it out.

These are the codes that we have in this vehicle. Right rear wheel speed sensor codes. There's an erratic signal and a low signal amplitude. So, we're going to drive this around with the scan tool and take a look. Okay, right rear wheel speed sensor. Let's put a couple of the other ones up, too.

Now, we can look at the values of the speed sensors while we're moving. So, here's all the values for the speed sensors. The one we're concerned about is that right rear one down below. As we move the vehicle, we can notice that right rear one is not moving like the other ones are. It's jumping around, but it's not exactly where the other ones are, which is important.

We already know we have an erratic signal coming from the right rear wheel. If you wanted to, you could have the scan tool monitoring the sensors, the wheel speed sensors, and turn the wheel. We already know from the test drive, so we don't have to do that. Now, we're going to take the wheel off and get a closer look.

We're going to take a look at the wheel speed sensor, and it's located right here. The sensor goes through this knuckle, and the wire right here. And what you could do is view the data on the scan tool, and turn the wheel, and try to manipulate the sensor wire, and see if you can get a skewed reading. See if something changes. A lot of times where the sensor wire moves a lot, there will sometimes be a break in that wire.

If you see right here, this is where the sensor goes through the knuckle, and it reads the backside of the hub. There's a ring on the hub that turns with the wheel, and that's where you get your reading. If you look at this side of the hub, you can see where this ring is. This is the ring and it's actually broken right there. And that's what's causing our problem.

You can see on this new one, this is how the ring is supposed to look. It goes all the way around. And if you look at ours, more than half of it is missing. It's just a little section right there. And this is what the sensor is going to sense, while the hub is spinning. The sensor is located right there and just picks up on that ring.

We replaced that hub, and now let's go for a drive and see if we fixed it. And here's the data for the right rear wheel speed sensor. I have also the right front up just so you can see a reference. Now, let's take it for a drive. And it should match pretty close to the right front. And it looks like it does. It's not skipping around like it did before, which is perfect. And our ABS light is out. We cleared the codes anyway, so we're good to go.

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