Do ABS units go bad?

[afroman006]

Every once in awhile the ABS light on my dash will come on on my 98 k3500. It always goes away though, and normaly breaking doesnt feel affected. A few times recently though, the brake pedal has randomly become rock solid and I am unable to stop. What gives? Is the ABS part a typically replaceable unit?

 

[daleearnhardt01]

Yes, I've heard it can go bad. However that part is quite expensive

 

[Leper]

Yes, they can go bad. But, the ABS system is seperate from the regular brakes. Even if the ABS goes completely out, the normal brakes will function properly.

 

[dhcomp]

I'm not sure if the normal brakes will funciton properly if the ABS malfunctions. For a while, in my 94, the ABS would engage on quick stops on dry pavement, when i was no where near locking up the brakes. After a few stops where the ABS took complete control and left me praying that i would stop in time, i pulled the power on the ABS box. When i disconnected it, the brake and abs lights came on, and when i reconnected it, the ABS light stayed on. Thus keeping a trouble code in teh computer telling it that the ABS is broken and not to use it or something. No more ABS And if i ever get in an accident, no one can put me at fault for "disabiling" or "bypassing" the system like others have done.

Moral of that long story is that if they do start to not work properly sometimes.

 

[daleearnhardt01]

Yes, they can go bad. But, the ABS system is seperate from the regular brakes. Even if the ABS goes completely out, the normal brakes will function properly.

Yeah my buddy's 95 2500 ABS doesnt work but it stops like normal...

 

[73k5blazer]

The light is trigger from bad wheel speed sensors too. That's what mine did.
Took alot of research, the dealer kept telling me the speed sensor only comes with the whole hub (even though it unbolts from the hub), and the whole hub was $600. But I finally got a part number for just the wheel speed sensor, $60 and ABS worked again. But the computer told me (after a scan) which part was bad. I knew it was left front sensor. So you might have it scanned to see what exactly the problem is.

 

[mini_mull]

My sister's 94 burb did the same thing as Darren's, she paid a ton to fix it, so I assume she got the whole hub. My 99 tahoe did it for awhile, too. Then, when we took off the crappy tires from the dealer (because the side walls had bubbled on 6 tires in less than 3 years) and replaced them with BFG A/Ts the problem just stopped.

 

[afroman006]

Well I replaced the master cylinder and hydrobooster and its still doing it. I didnt really expect it to stop but they needed to be replaced anyway. Do you have part numbers for those sensors? I scanned the trucks puter with my little actron scanner but it didnt have a single code on it, and the problem still persists. Does this need a more elaborate scanner or just to replace those sensors? I know exactly what you are talking about because I recently replaced the my front rotors so I had those hubs off anyway.

 

[73k5blazer]

Yeah, you need to full dealer tech 2 scanner to see it. If the light is on, there's a code there. You might get lucky and it could be the one screwed into the transfer case for the rear, that one's cheap and easy.
I'll dig out the hub sensor number for you. Give me couple of hours here. Your 98 3500 should be the same as my '97 2500HD. Only differece between the 2, should be you got borg-warner t-case and larger rear brakes. When I bought my truck I looked into that, I was going to get a 3500, but found the 2500hd was pretty much the same, spring part numbers, torsion bar numbers,were a match between the 2.

 

[73k5blazer]

Sometimes those sensors just need a cleaning too.There were a couple of tech bullitens on that.
Measure AC voltage and clean wheel speed sensor mounting surfaces.

1. <LI type=1>Raise the vehicle on a hoist. <LI type=1>Disconnect both the front wheel speed sensor harness connectors. <LI type=1>Place a DVM across the terminals of each sensor connector. <LI type=1>Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's. <LI type=1>If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor. <LI type=1>Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service. <LI type=1>Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite™, or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion. <LI type=1>Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor. <LI type=1>Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218). <LI type=1>When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037). <LI type=1>Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub. <LI type=1>Install the rotor, the caliper and the wheel.
2. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's.

Parts Information

Part Number

Description

89022217

(Canadian P/N 89022218)

(Package of 2 cans)

Rust Penetrating Lubricant

(Each can will service 50+ vehicles)

01051344

(Canadian P/N 993037)

(Package of 12 tubs)

Wheel Bearing Lubrication - Tub

(Each tub will service 25+ vehicles)


Place unused material on dealer shelf for future use.
">Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

H9714*

Front Wheel Speed Sensor Inspect and Clean (Both Sides)

1.2 hrs

 

[73k5blazer]

The left front wheel speed sensor is:15991985
Right front is 15991986

$60 each on gmpartsdirect.com or $102 at the dealer.

never looked up the rear one that screws into the t-case.

 

[afroman006]

You da man.

 

[73k5blazer]

Yeah, the trouble with the dealer at the time, about 3 years ago, the computer didn't call out on the illustration the wheel speed sensor. He couldn't look it up in the service parts system by words either. I was like, that's BS, I'm not paying $600 for a hub when I know there's got to be a service part for just the sensor.I recruited a GM insider I know to find the part number, put it into gmpartsdirect.com and presto. Mabey service parts have fixed their illustrations by now.