Antilock Brakes kicking in at Low Speed on Dry Pavement?!

[ScottS]

Stefko

You are correct the abs system should be disabled when below a certian mph - problem is, when the speed sensors malfunction, the van has trouble determining what that speed is.

I think , in hindsight, what happened to me was, the failed sensor allowe the ABS to kick in at around 5mph - and since I was 2 feet from a building, I took both feet and pushed for all I was worth and I popped the brake lines, which were rusty.

[blk lt awd]

i just got my van insured and fired it up for the first time last night since last year......my abs light also came on when i applied the brakes to take it for a spin around the block......now i'm sure it's just a cleaning that's needed to clear that up however if one of the sensors are bad anyone know how much it is to replace?

also anyone know if we can still go through air care in the lower mainland if the light is on?

oh, one more thing, so to clairfy....the front sensors on the AWD's....to get at them...we need to remove the rotors.....then is there is a cap in the middle of the hub with the lugs where the bearing would go and in there is the sensor????? is it in front of the bearing or behind it? is that not filled with grease?

[LiftedAWDAstro]

oh, one more thing, so to clairfy....the front sensors on the AWD's....to get at them...we need to remove the rotors.....then is there is a cap in the middle of the hub with the lugs where the bearing would go and in there is the sensor????? is it in front of the bearing or behind it? is that not filled with grease?

Yes you will need to remove the rotor. The sensor is between the 2 bearings. These are non-serviceable unit bearings. The sensor is bolted to the hub unit bearing housing. You may need to remove the hub unit bearing to get at the sensor. The bearings have grease on them but the sensor should be fairly clean.

[stefko]

I just found this Googling,"testing speed sensor astro van 2000.

I have a 2000 astro cargo van AWD with 4.3l and 163000 mi.

Sent to Chevy Experts November 07, 2007 8:22 a.m.

I have a 2000 Astro cargo van AWD with 4.3l and 163000 mi. no codes set. when going forward or reverse (less than 10 mph)and slightly pushing the brake pedal the abs will intermittently activate. With the scan tool hooked up the wheel speed sensors are changing state like they should, and you can see the abs come on. What would cause this? thanks.....Customer (name blocked for privacy)



Hi Customer (name blocked for privacy), This is a common problem with 4 wheel drive pick up trucks but also happens to AWD Astro vans. The problem is that there is rust building up under the front wheel speed sensors. When this happens the air gap increases and the speed sensor will send a signal that is incorrect causing the ABS module to think the wheel is locking up. To repair this you need to remove the speed sensors from the front wheel bearings. Now sand off the rust where the speed sensors mount, apply grease so it won't rust again and reinstall the sensors. Sometimes the sensors will break when you try to remove them from the wheel bearing. If this happens you will need new speed sensors.


I hope this is helpful to all!!!!!!!!!

[safariobsession]

I've got this same type of problem on my 2008 Chevy Express work van. It happens at least a few times a day, only at low speed when almost stopped (under 10 mph). It is definitely the ABS kicking in but I wouldn't think the rust buildup issue would be the problem in my case, on a van with only 18,000 miles. Most if the ABS issues i see pertain to late 90s early 2000s silverados too. I'm about to call the dealer to see if there is any kind of bulitin/recall. I'm about to yank to ABS fuse since a couple co-workers had scary experiences driving my work van.

[mattblackratbus]

My ABS did'nt work for ages then i fitted a new sensor and got it working, after a test drive i wondered why i bothered. I hated the feeling that the van was helping me brake, so i pulled the fuse and removed the warning light from the dash for the m.o.t test. Now if i need to slow down quick i do what my driving instructer taught me, if i crash then its driver error ...Johnny

[SafariRob]

My ABS did'nt work for ages then i fitted a new sensor and got it working, after a test drive i wondered why i bothered. I hated the feeling that the van was helping me brake, so i pulled the fuse and removed the warning light from the dash for the m.o.t test. Now if i need to slow down quick i do what my driving instructer taught me, if i crash then its driver error ...Johnny

Thanks for that, Johnny. What a breath of fresh air. Way back in 1968 I was in Driver's Education and we were taught to modulate the brake pedal with our foot during a panic stop to maintain steering. Much later, some legislator decides that I can't handle doing that, so electronics are mandated to do it for me. However, it's left up to each of us to find out what the dark side of ABS brakes are. In my case, it happened on a snowy day in my company truck, a 2003 Dodge 3500 van. As I came up to stop at an intersection, the ABS kicked in. Abruptly, as I was slowing, the brake pedal went to the floor. I got a mega dose of adrenaline, instinctively pumped the brake pedal and regained braking, but the van's nose was well into the intersection by then. Fortunately, no one was coming, so it was just me and my truck looking stupid stopped in the intersection. I've never fully trusted the ABS system on that Dodge since then.

[risteff]

Looks like I'll be digging in to the abs issue too. Just about hit my Wife's suv when I pulled into the driveway tonight after work. It was under 5mph. The pedal went to the floor and had a little abs motor feedback. If I hadn't put my 2000 Safari into nuetral, I would have torn it up. This is my only driver right now, so I'll pull the fuse until I can get to it. Thank you all for the posts and info. You may have save someone's life or at least their bank account!

[morkman]

Well, this just happened to us very recently (97 Safari AWD), but it was almost immediately after having had the front brake line from the ABS pump replaced. I noticed a previous poster mentioned that it happend to him after having replaced brake lines etc.
I'm wondering if there is a possibility that improperly bleeding the whole system after replacing an ABS line is possibly the problem. The ABS light did not come on when this occurred, although it is now with the fuse removed...lol
I would like to explore all possibilities before spending $275 per wheel to replace bearings and sensors

Cheers

[risteff]

I would hesitate to say this has to do with improper line bleeding. I have dealt with several types of ABS units (mainly the Kelsey Hayes on the early 90's vans) and have found that improper bleeding or air in the ABS unit will result in a very soft pedal all of the time. I have not yet replaced the hub bearings / sensors on the front of my 2000 and still have the ABS fuse pulled. I recently popped the long front to rear brake line, replaced, and bled it & I still have a rock solid pedal. I am not a brake technician, so you may want to consult one. There is a special tool you are supposed to use to bleed ABS systems after master cylinder or ABS unit replacement. Anything in the system after that is bled in the normal fashion. Pull your fuse for now just to be a little safer and good luck!

[morkman]

Thanks for the reply....at this point, our mechanic can't tell us which front sensor ( and bearing) has to be replaced.
Apparently there is no code identifying an ABS problem on a specific wheel.
Any magical trouble-shooting suggestions would be greatly appreciated.

Cheers

[kamenz]

Well if it is the bearing you usually can tell by the play in the hub wheel assembly. Just raise the front end with the wheel mounted and check for excessive play.

[MountainManJoe]

Whichever side the van pulled towards.