ABS light and Parking Brake light staying on

RickT4098 · October 13, 2016

2004 GMC Sierra 2500 HD

I have a problem I will just first explain what happen, My Friend ask me to see if i could tell where the squeaking sound was coming from on one of his rear wheels, So I took off the wheel and hub and sprayed brake cleaner on the brake caliper and brakes, I did not remove them. And just did the side he said the noise was coming from.

So then I test drove the car for around a mile and did not hear a sound after spraying cleaner on that one rear brake and caliper.

here is the Problem I live on a hill so I was afraid to just leave it setting without putting on the parking brake which is in the floor...

That is when the problem began, after driving it the next day up the road, I noticed the abs light and brake light was flickering off and on... then eventually both stayed on and now they will not go off.

I thought this has to be a parking brake switch issue since that was all I did it push in the parking brake.

I tested it today and it is only one ground wire going to the switch, so I hooked up my test light to the metal on the switch and the other end to a positive wire

when i press down on the parking brake the light on my test light comes on... when i release the parking brake after some adjustment of the switch so it will get good contact with the parking brake the light goes off when released.

But still the abs light and the parking brake light is on... Do you think the switch still could be bad? cause I do not know what else could of just happened just by merely pushing in the parking brake to keep it from rolling down hill.

Any Advice would sure be appreciated... Thank you

txab · October 13, 2016

Have the codes read that are stored. To rule out other things

Formulabruce · October 13, 2016

Rear abs sensor has guk in it due to the moist cleaner collecting brake dust

I assume you are talking about just ONE vehicle in the original post? ( yours or your friends?)

May need a rear wheel seal, so check pads and back of backing plate for any rear end oil..

RickT4098 · October 13, 2016

Hello thanks to you both for replying: I had checked the codes when this first happened and was getting the code U1041 means that the other computers have lost communications with the EBCM.

Then I cleared the code to see if it returned, so far the code has not returned but it also did not help in the abs light are the parking brake light to go off.

and yes talking about my friends it is a 2004 GMC Sierra 2500 HD

I do not think it has abs sensors in the rear cause there is no electric wire going to either side of the wheel in the rear?

so when I seen they did not have wires going to them I assumed like another truck I had worked on before which was a Ford Ranger that the rear sensor was in the rear differental.

and like I said it is strange after cleaning only the rear passenger side brake and rotor off which was the side he said was making the noise, I test drove it and it was fine ... Then when I came home I put in the parking brake and the next day driving it the two lights started blinking, and now there on all the time.

RickT4098 · October 13, 2016

any other ideals?

davester · October 14, 2016

that switch only turns on the parking brake light. even if it fails, it doesn't cause the abs light to go on.

It may be that the ground for the ABS computer needs cleaning/fixing. It is located on the 'wing' off the frame, right under the drives door. There are two bolts holding two connectors to the frame, take the bolts out, clean both the frame and the connectors down to bare metal, put on a bit of dielectric grease on the connectors, then bolt them down again.

RickT4098 · October 14, 2016

ok only thing i did not do is put dielectric grease on them I had cleaned those two connectors though used my drill and a grinding wheel to take them down to metal instead of the rust that was under them but that didn't help either. I even ran a ground wire from a good ground on top of engine to each of the two on the frame under drivers side and still no luck...

RickT4098 · October 15, 2016

IT sure has me in a bind. I have done everything I know to do. I have cleaned the two wire connector at the drivers frame twice all the way to metal.. and even ran a good ground wire to them to be sure they were getting ground.

It just is hard to understand why just mashing in the parking brake would cause these lights to come on and stay on... I have a good scanner tool for abs and so forth and it is not picking up any codes at all.

He ordered a new parking brake switch but I do not think that is the problem either it is suppose to be here Monday.

the fuses are all good.

I would not think the abs module would go bad just by mashing in the parking brake to hold the truck on a hill.

Formulabruce · October 16, 2016

Time for a pressure bleed in the rears...

RickT4098 · October 17, 2016

bleed the brakes in the rear? the brakes seems to be really good I do not have to pump them to get brakes?

today I took the two abs sensors off the front and cleaned them and make sure the reluctant wheel was good on each wheel

went under the truck and checked out the parking brake cable to see if there was slack in it with parking brake off and there was.

checked under dash for any lose wire... Nothing there.

checked ground wires again seem fine also...

Lord only knows what is wrong I sure do not.

davester · October 17, 2016

So the ABS & brake lights are on, and you have a code reader that can at least scan ABS codes, and there are no ABS codes?

A regular ODBII code reader doesn't read ABS codes.

Formulabruce · October 18, 2016

Low pressure ( why I mentioned a pressure bleed) and a rusty ABS unit ( in frame under DS seat) can cause issues like this. The ABS unit can leak and pedal feels fine till it blows a rusty line...

GMmaniac · October 18, 2016

Have a family member that has this on Chevy 1500, emergency brake problem and I believe they had to cut the emergency cable..

davester · October 18, 2016

There is NO way the emergency brakes can cause either the ABS or parking brake light to go on. It is literally a completely separate system from the regular disc brakes.

The switch on the parking brake pedal mechanism is the ONLY electrical connection for the entire emergency brake system.