Abs problem

[Feral peasant]

98' Chevy k2500 HD 5.7 vortec, the abs light was on before but a code came up for a speed sensor. Recently the lights been going out and my abs is acting up worse than it usually did, I'll press on the pedal and the pedal will start forcing itself back up and unlock the wheel also this happens lower speeds around 30 mph almost hit a person crossing the road because of this. When the pedal goes back up it starts taking pressure off the wheels and i can't stop. It's been rainy here for a couple days and this is when it's been worst any ideas? I think my back wheels are locking (drum brakes might be going out?) I also hear the activation of my abs sometimes and it's loud what could it be?

 

[Caman96]

Sounds like you don’t have a stock brake system then, unless you are mistakenly calling the rears “DISC” brakes. Or did the HD 2500’s get disc brakes. I thought only 3500’s got rear disc.

 

[Feral peasant]

Sounds like you don’t have a stock brake system then, unless you are mistakenly calling the rears “DISC” brakes. Or did the HD 2500’s get disc brakes. I thought only 3500’s got rear disc.

My fault the rear are drum brakes

 

[Caman96]

I’d start with a complete front and rear inspection, replace anything needed, replace wheel speed sensor(s) and see where that gets you. Also, bleed the system, quite possibly your ABS system needs to be bled too.

 

[Feral peasant]

I’d start with a complete front and rear inspection, replace anything needed, replace wheel speed sensor(s) and see where that gets you. Also, bleed the system, quite possibly your ABS system needs to be bled too.

Honestly this is my first vehicle and it was rednecked a bit so I don't fully know what everything should look like, I'll give a shot to bleeding before I spend money (I'm broke) if that doesn't fix the problem then new speed sensors. I'm guessing the sensor wire is the one that runs right on the frame to the wheel?

 

[fancyTBI]

The wheel speed sensors connect to the ABS module via a connector on the side of the module closest to the drivers fender. Follow those wires. On 2wd trucks they run from the ABS, to the frame, split (one sensor wire goes to the driver sensor attached to the dust shield, the other runs along the cross member, to the frame rail, to the sensor on the dust shield). In K trucks I believe it follows the brake lines under the core support.

 

[Caman96]

Honestly this is my first vehicle and it was rednecked a bit so I don't fully know what everything should look like, I'll give a shot to bleeding before I spend money (I'm broke) if that doesn't fix the problem then new speed sensors. I'm guessing the sensor wire is the one that runs right on the frame to the wheel?

Your truck is literally telling you there are issues. ABS light and speed sensor code. Doubtful that just bleeding the brakes will resolve everything. Remember, to bleed air out of ABS, you’ll need a scan tool capable of doing that.

 

[Feral peasant]

Your truck is literally telling you there are issues. ABS light and speed sensor code. Doubtful that just bleeding the brakes will resolve everything. Remember, to bleed air out of ABS, you’ll need a scan tool capable of doing that.

The light was on for the speed sensor, but it's just gone off for some reason the speedometer is still reading speed but incorrectly ( was doing that before it went off too) but my next off day without rain I'll see what I can do to bleeding and check the connections for the speed sensors thank you

 

[fancyTBI]

The speed sensor is on the hub. It has nothing to do with the speedometer in the way that you are thinking. Speed sensors are sensitive. If rust causes the mounting surface to bulge the readings can be thrown out of spec. Damaged wiring is another common issue. Or the sensor itself has failed. Your ABS will activate if the right (even erroneous) conditions are met. Bleeding the brakes likely won’t help with this issue.

 

[Feral peasant]

The speed sensor is on the hub. It has nothing to do with the speedometer in the way that you are thinking. Speed sensors are sensitive. If rust causes the mounting surface to bulge the readings can be thrown out of spec. Damaged wiring is another common issue. Or the sensor itself has failed. Your ABS will activate if the right (even erroneous) conditions are met. Bleeding the brakes likely won’t help with this issue.

Alright I'll definitely take a look at those connections and everything stated above, seems like this might have me doing a full checkup on the brake system thank you