ABS light winks

[Daren]

Hi Eric and happy Thanksgiving,
For a few weeks, maybe even months, my ABS light comes on and goes off on occassion. Sometimes it will do this when I back out of my driveway and I feel/hear a growling sound and my brake pedal sinks a little deeper towards the floor. My 2002 Silverado, equipped with four-wheel disc brakes, still stops and when I shift into drive and pull away, the ABS light will go out within a block.

My truck has 186,000 miles and I have not experienced any ABS issues. The only brake work I have had to perform on this truck involved pads, rotors, and parking brake shoe replacement. This is just routine wear-out stuff. Back in the spring I did a four-wheel brake job and I even flushed out the old brake fluid in the process. It has worked well until this ABS light came on recently.

The first thing I plan to do is to check the ABS sensors to see if any wire is broken, if any connections and dirty and clean them, and plug in my ODB scanner that is also capable of checking ABS codes. I have yet to use this functionality of my OBD scanning tool.

My question is does this symptom sound like a defective ABS wheel sensor? The ABS light will come on and off while I am driving. Sometimes it stays on longer, but it always goes off and my truck brakes the same with the exception of what I described when backing out of my driveway sometimes.

It appears a wheel sensor is around $30 on Rock Auto, but as cheap as that sounds I still want to diagnose the problem before committing to purchasing any parts.

Am I even on the right track here? I haven’t had to mess around with ABS systems. They seem to be relatively trouble free. Maybe age and mileage has caught up with my Silverado.

Thanks for your input Eric,

Daren

Topic

[John Hugon]

I’m not Eric or even close to Eric’s knowledge, but I’ve worked on a few Chevrolets in my day. The first thing I would do is try to scan the abs module for codes than diagnosis from that point. Let us know what the codes are and someone will help you.

[Daren]

Yes, I plan on plugging in to get an ABS code. I hope that I can get some sort of a reading even if the ABS light is off. This is an intermittent issue. The truck stops as it should, but I know the ABS system has a problem.

A few years ago I replaced one of the front hub bearings, so I might have the hub bearing to consider. The one I had to replace was growling on turns and the ABS light never came on and I did not have any brake symptoms I am having now.

I want to think this is caused by a bad sensor, but I plan on finding out this weekend.

Thanks for following up. I’ll post my findings.

[John Hugon]

The one I had to replace was growling on turns and the ABS light never came on

That’s a common issue with that truck….I bet that bearing was hard to get out….

[Ingvar]

Front hub bearing on Silverado, at least on 99 and younger, takes about 10 minutes to replace. As far as you have LARGE tools, those trucks are very easy to work on. Moistly. Headlight assy takes less than a minute to remove.
Anyway. OP, remove wheels, and remove ABS sensors. CLEAN them. They are well known to corrode and cause intermittent ABS light. You can even replace them, easy access and plug’n’play swap.

[Daren]

Yeah the hub bearing we replaced about four years back wasn’t complicated. We had to heat up some of the bolts to get it apart, but it wasn’t a big deal.

I drove it today and the light never came on. I am going to plug my code reader tool in and fish for a code. I am also going to clean the connections. I also saw where applying some dia-electric grease on the terminals is helpful.

I don’t think I have a bad hub bearing. I don’t detect any of the symptoms that occured when the hub bearing went bad the last time.

[John Hugon]

Front hub bearing on Silverado, at least on 99 and younger, takes about 10 minutes to replace

In the rust belt not so…they rust in… I’ve got a secret to do them…if you look hard enough its on u-tube

[Ingvar]

Not the CONNECTIONS. The sensor contact area itself. THAT does rust or oxidize.

[Bill]

Trucks like yours have a very well known issue with front wheel bearings and ABS sensors in climates where salt is used on the roads in winter.

Rust builds up between the sensor and the wheel bearing and increases the distance between the sensor and the tone wheel inside.

I have had limited success with removing the sensors and cleaning the surface with an abrasive and reinstalling the sensors.

That said, the ABS usually activates at very slow speeds when this is the problem however.

[Ingvar]

ABS does not activate at speeds roughly below 10 mph. Not sure what “very low” speed is.

[James O’Hara]

I am with wysetech on this one. Pull the sensor out of the holder and clean the face with a wire brush. Then clean the tone ring with a wire brush then shove the sensor back in until it contacts the tone ring. the tone ring will either be on the back of your rotor/drum, on the axles, or inside the bearing. Here are some tone ring pictures:

Tone ring on a half shaft:

Tone ring inside a bearing:

Tone ring on a rotor:

If the tone ring is inside the bearing I would suggest a new bearing but, I doubt it is on a truck. While you are under there look around for nicked wires and/or corroded connectors but, my bet is on the tone rings in this case. If your rule that out and you want to see some other stuff on checking the abs system there is my post on this persons problem: http://www.ericthecarguy.com/kunena/8-Service-and-Repair-Questions-Answered-Here/54820-help-noisy-clunking-noise-could-be-abs-sensors

[Daren]

We checked using the ABS scanner and it indicated the driver side sensor was faulty. This is the side with the replacement hub bearing, so I am surprised it was the sensor on that side.

I might just go ahead and spend the $30 for a new sensor if I have to take it all apart to check/clean it anyway.

The scan tool also indicated an issue with the stop light switch, so I might go ahead and get one of those for another $18.

I drove it today and the light never came on the the brakes operated as usual.

[Ingvar]

Just a word from ex Silverado owner – and ex about 6 Silverado forums member.
MANY fixed their ABS light by simply cleaning the sensor contact surface.
Btw, pulse ring is inside the hub bearing. You can’t clean it from the outside. Sensor is monitoring it via provision in the hub itself and is super easy to remove. Be VERY careful with wire though, as it goes into very sharp turn clip holding it in place. Easy to damage.

[Bill]

Obviously, you’re the expert. You should know what very slow speed is.

[Daren]

Maybe I should try to clean it as ukrkoz suggests. The sensor that is acting up is the one from the replacement hub bearing.

I live in Nebraska so there is a good chance the weather (road salt use) could be a factor.

The light comes on intermittently and doesn’t remain on for very long. So maybe the sensor can be cleaned and re-used.

I appreciate the input I am receiving. Thanks everybody. I’ll post the results.

[John Hugon]

ABS scanner and it indicated the driver side sensor was faulty… also indicated an issue with the stop light switch

As a suggestion…so you don’t replace good parts…the scan tool points to the direction of your issues. If the scan tool indicates L/F wheel speed circuit, the next step would be checking that circuit including all bulletins issued about your concern. Eric has a very good general way of checking circuits in his web site.

Some factory TSB’s come to mind on your ABS concern; ABS sensor mounting rust issue as pointed out, worn/loose front wheel bearing as pointed out, moisture intrusion into connectors and wire breakage…even under the insulation.
Brake light switch….if I remember was a issue in that year …along with other model years because of a bad design.

[Author]

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