ABS ocassionaly activating when braking

[johnholl]

Any ideas? Binding caliper or slide pins? very odd. No dash lights triggered.

[maxwedge]

Could be a bad wheel speed sensor a road test with a abs scanner connected can watch wheel speed inputs to see which one may be bad.

[Tech II]

Occasionally activating? Does the ABS light come on when this happens?

Like Max says, if a code is set, it will at least direct you to one of the four wheel speed circuits that may be at fault.....notice I said circuit, not sensor....that means ANYTHING in that circuit....

If the light is not coming on, and no code is set, that is a tougher scenario to diagnose....

[SleepyHead98]

Well.. If one wheel is getting more pressure than others it will lock, triggering abs. might try bleeding brakes as a starting point.

[maxwedge]

The only thing that normally triggers the ABs is a marked difference in wheel speed input such as one or 2 wheels locking, lower or higher pressure is not the issue unless it causes wheel lock.

[SleepyHead98]

Right, But if he has air in the system on three wheels, but not the one that is locking, then it would need to be bled.

[Tech II]

If he has air in the system, then he has a leak....you fix the leak, you don't bleed the system first....

Intermittent ABS activation is usually cause by a signal problem, usually due to a speed sensor or wiring harness problem....

[SleepyHead98]

Like I said, So as a starting point, bleed the brakes.

One thing I have learned from being on this forum, Is we never know what the poster has done to the vehicle before they ask for help. For all we know, they could have opened all the lines up, and unwittingly let air in. Not saying this is the case. We just dont know.

[johnholl]

Originally Posted by SleepyHead98

Like I said, So as a starting point, bleed the brakes.

One thing I have learned from being on this forum, Is we never know what the poster has done to the vehicle before they ask for help. For all we know, they could have opened all the lines up, and unwittingly let air in. Not saying this is the case. We just dont know.

No, haven't opened the bleeders. No, the ABS indicator does not activate. I may check and clean the speed sensor connectors. I fear that these speed sensors are integrated into the hub assemblies, and thus costly to replace. More of an occasional annoyance at this point.

[SleepyHead98]

Yeah typically they are. Depends on the vehicle you have as to the cost to replace. Some people will be adamant you buy timken hubs, others will say stay away from china made hubs. Personally, If your budget does not allow you to buy usa made hubs, buy what you can. Whether that be ebay or whatever, just be sure to torque the cv axle nut correctly on the front wheels, as this will lead to premature failure of the hub.

I bought MAC hubs from ebay for my 98 olds cutlass, 100 bux for a pair as I don't have any extra spending money, this was my only choice. Good luck.

PS. I would still bleed the brakes if you havent done so in the last two years.

[Tech II]

Sleepy, you have bleed the brakes on the brain .....I have never solved an ABS problem, by bleeding brakes......only time I have bled brakes, is because of a leak, a repair, or just replacing the fluid....

[SleepyHead98]

Probably, but I like to start at the lowest cost easiest fix. Brakes probably need to be bled anyways, and if there is air in system, he will figure that out real quick.

[johnholl]

Originally Posted by Tech II

Sleepy, you have bleed the brakes on the brain .....I have never solved an ABS problem, by bleeding brakes......only time I have bled brakes, is because of a leak, a repair, or just replacing the fluid....

I'll check the sensors when I get a spare minute. A previous post indicates 180 ohms. I'll check the condition of the wiring as well.

[Tech II]

850-1350 ohms.....

[Gabito72]

Hi
I have had that problem on the past on my 2005 equinox. It could be a loose sensor. Check if every wheel sensor is well installed on its bracket, if not, hang wires can be chewed when you rotate the wheels. That was my case.... It was easy to fix it.
I had the same problem with my 2003 Pontiac Grand Am GT
I hope this helps.