Abs problem with chevy dually

It appears to be a known issue with faulty brakes on Hyundai vehicles.

https://www.google.com/search?q=2010+Hyundai+Getz+intermittent+brake+failure

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check: fluid level, brake reservoir filler cap for proper fit, brake level safety switch connection wires on master cylinder or reservoir cap that they are snug. If those are ok the brake light suggest an intermittent failure in the primary chamber when fluid is bypassing the seal. This is usually a accumulation of debris on the floor of the chamber. Changing the fluid is a start which should include a removal of the master cylinder, extracting the piston and inspecting the interior of the cylinder for sludge. clean out the sludge avoiding scratching the cylinder walls. reassemble, reinstall and bleed system. The ABS is likely related to the primary failure and should clear. The ABS light is likely telling you that the brakes are unevenly being applied and that the ABS diverter is being activated--as it should be.

You need your vehicle checked with a scanner that reads ABS codes. Not all scanners can read ABS codes. Most likely it's an ABS wheel sensor that's bad. I've changed a few of them on 02 & 03 Explorers.

Good luck.

check the clearance of the brake pedal rod into the master cylinder. Should be about 1" movement before the rod moves the piston .
The master cylinder has a blockage in the compensating ports so replace the master cylinder. As the brake oil is heating from brake application, it is not getting back to the reservoir so it is pressing the pads back onto the rotors which is heating the oil even more.

You have a defective master cylinder.

I am in the UK, so do not know this model, but I am a Bosch service tech and can tell you, if you have air in the ABS unit itself, you well need to connect to diagnostic tool with bleeding/venting program on it. The ABS pump needs to run and operate the solenoids to get the air out...

sounds like the anti lock pump is gloing out

is the abs light on?the abs system only effects the pedal when you are stopping quickly to activate the system. you still have a hydrualic brake pressure problem. are the rear brakes shoes or pads? rear shoes out of adjustment can cause a low brake pedal.even though the master cylinder has been replaced doesn't mean you got a good part.if the part was a remanufactered part very likely it is bad. to determine if it is the master cylinder, plug off the lines from the side off the master cylinder and hit the brake pedal. if the pedal stays up look for a problem elsewhere in the system. if the pedal drops the the master cylinder is defective.

I think you have one wheel sensol that gives wrong speedsignal. This will activate the ABS in slow speed.

CHECK BRAKE FLUID LEVEL MAKE SURE MASTER CYLINDER IT HAS CORRECT AMOUNT OF BRAKE FLUID IN IT.IF YES MASTER CYLINDER IS FAULTY OR AIR IN BRAKE SYSTEM.IF YOU CHECK BRAKE FLUID IN MASTER CYLINDER AND ITS LOW .CHECK FOR LEAKS AT BRAKE CALIPERS SEALS AND BRAKE HOSES. CHECK ALL WHEEL CYLINDER SEALS AND BRAKE HOSES AND ALL BRAKE LINES.