ABS kicks in on when it shouldn't

ghorty · March 21, 2017

I just started having an issue where my ABS breaks kick in when it shouldn't. I have noticed it happen mostly when backing up or down grade, and then doesn't turn off until I take it out of Drive. I have also had this happen when parking in a dry parking lot, so no reason it should kick in. There are no error codes being generated by the ABS. When it does kick in, I noticed the brake peddle clicks when I press it.

Anyone else have this or any ideas what's causing this?

2016 Silverado Z71

It's Tim · March 21, 2017

Same size tires all around, proper inflation?

ghorty · March 21, 2017

Yes, original tires, all 34-35 psi, 16k miles on the truck so far.

Andy Seibel · March 21, 2017

This sounds very strange. When the ABS activates, it actually releases pressure on the brakes to allow the wheels to turn. if this were to happen while you are rolling on dry pavement, you should have problems stopping. Can you feel the pulsing? the ABS pulses and you can feel it in the brake pedal.

When you hit the brakes is the truck stopping faster or slower than you want it to?

Your issue isn't with grade braking is it?

2strokesmoke · March 21, 2017

Under a set speed say around 20 mph abs engagement should not activate, locked out by either speed sensor, or abs wheel sensor. If you hear it cycling or notice your breaking is reduced at low speed stops, have it checked as this can be very dangerous and is not operating normally!

Best of luck

ghorty · March 22, 2017

This is all under 20 MPH. I am bringing it back in. I just wanted to check if anyone has heard of the issue before so I could give them better detail than it happens from time to time that ABS kicks in and doesn't throw an error code.

Andy Seibel · March 22, 2017

I'm not certain that 20 mph is the correct limit. I have my ABS activate all the time when I'm plowing snow, trying to stop on ice. And most of that occurs under 20. so the actual limit may be much lower.

But the key is when you apply brakes and the wheels suddenly & immediately stop spinning, the system thinks you are still moving forward so it releases the brakes to help you gain traction.

If the system is engaging when your wheels are still rolling, there is something wrong, and I agree you should take it in.

2strokesmoke · March 22, 2017

I'm not certain that 20 mph is the correct limit. I have my ABS activate all the time when I'm plowing snow, trying to stop on ice. And most of that occurs under 20. so the actual limit may be much lower.

But the key is when you apply brakes and the wheels suddenly & immediately stop spinning, the system thinks you are still moving forward so it releases the brakes to help you gain traction.

If the system is engaging when your wheels are still rolling, there is something wrong, and I agree you should take it in.

It may vary well be a lower speed engagement, but the principle is the same should not cycle at low speed!

Have it checked!

ghorty · March 23, 2017

It's in the shop right now, the ABS even kicked in as I parked it in the service garage there. Have not heard any follow up yet. Will keep it updated for anyone else who runs into it.

ghorty · March 23, 2017

Just got off the phone, the dealer was able to replicate it today while in the shop and they are talking with GM on the issue. They are giving me a rental until as they dig deeper into the issue. Progress!

Andy Seibel · March 23, 2017

glad they could see the issue. that's half the battle.

paumat · March 23, 2017

This was a common issue on the 99-02's and there was a recall for it. I can't remember the exact cause but I believe it was corrosion on the wheel speed sensors.

SILVER SLED · March 24, 2017

The cause from the recalled older trucks is because the flat mount portion of the wheel speed sensor that mounts to the hub would be raise up by rust on the hub pushing up on the sensor causing an out of spec reading from that sensor causing the abs to activate at slower speeds...hope that makes sense. This never set a code either, but if the vehicle is drive with a scanner set to observe the sensors, you can see a sensor(s) drop out/display 0mph wheel speed. A bad sensor can cause this also. It shouldn't be that complicated. Hopefully for you the problem is that simple and an easy fix.

2strokesmoke · March 24, 2017

Gonna take a guess that a speed sensor, or a grounding issue is causing your headaches!

ghorty · March 24, 2017

When I picked up the rental they were talking to GM on it, and might not get an update until Monday, we will see. I hope it didn't rust in less than a year that I owned the vehicle.

And yes, I was ecstatic when they said they replicated the issue. That was the issue with the 2014 Silverado I turned in with the steering vibration. They would not admit they could replicate the issue. I traded the 14 in on this one before the manufacture warranty went out on it.