99 Blazer LS Question

[dmbrisket 51]

my truck doesnt do the 3mph thing and my abs work fine, in fact, i just went about 5 mph into my driveways snow pile, and i know they are working

[Turbocpe]

Perhaps it doesn't affect your charging system to the same degree. But it does cycle the pump for a brief second at 3MPH. If it didn't, it would set a trouble code and the ABS light would be on.

Edit, by the way, your vehicle must be moving 8 MPH or greater or the ABS system doesn't work, according to the GM factory shop manual.

[dmbrisket 51]

shit, my truck doesnt see 3mph, lol that brief split second on its way up

[Turbocpe]

I should state that as far as I understand, this occurs once the speed hits 3MPH or greater. So while you're passing the 3MPH mark, it will occur.

The manual states that you may hear this noise in the engine bay when it occurs. But other than that, you will not know that this occurs because the pump can run and not affect normal vehicle operation while it runs this brief test.

My truck does this every first time I hit 3MPH or greater. At night, I'll see the lights flicker, in additon to almost a crush type sound.

[dmbrisket 51]

ive heard it b4 while strip crusin, so yeah, i guess it does it, kind of nifty... so the one time my abs light came on, the test failed? correct? why? and why only once?

[Turbocpe]

There are many things that could fail which would turn on the ABS light. So honestly, no one could tell you why your ABS light was on one day. The only way you could know is if you had the computer checked for trouble codes. There are different degrees for certain faults. If it only occurred one time, and that has been a long time ago, I don't know if the abs computer would still have a record at that point of the cause. Someone more knowledgeable of this particular system would have to speak about it.

[dmbrisket 51]

its nothing that did or does worrie me, it happend once, back in augest, right when i got it, and thats it, all it took to fix it was off then on again, but hey thanks, i learnd something new today

[deadeye]

I think I may be seeing the flicker shortly after start as turbocpe describes, but I wouldn't say it happens everytime, but maybe I'm just missing it. But it also occurs at other times whether anything else is running or not.