[morpiest]

I’ve been having this issue i haven’t seen anywhere else on the forum where at low speeds and with the brake pedal depressed more than halfway, it begins to stick on the way down but always returns to the top end no problem. only happens when coming to a stop and at 3mph and under. all the wheels spin freely when lifted in the air no lock up. it’s mainly just annoying the truck stops just fine but it can become worrying when you’re trying to stop and it feels like the pedal won’t depress any further but it just needs more pressure to get past whatever is restricting it. at times, and mostly when the front wheels are fully turned to the lock, it will activate abs when the pedal sticks and you’ll hear the crunching noise, and will disengage when the pedal is depressed more.

 

[Ravalli Surfer]

Your ABS is angry because it's being lied to by a wheelspeed sensor.

 

[Mark156531]

I have almost this exact same issue. I thought maybe the brake pedal needed some lubrication, but I haven't given that a try. I also get that vibration like the anti-lock brakes are kicking in. It most happens on slow hard turns.

 

[Ravalli Surfer]

Wheel speed sensor.

Really.

It is!

 

[Mark156531]

How do you determine which wheel speed sensor has gone bad?

 

[Ravalli Surfer]

Aha? Now comes the correct question!

A good scanner should be able to read wheelspeed, individually and dynamically.

An Ohm meter might find high or low resistance in each sensor

An oscilloscope can see a bad digital signal.

Physically inspecting the wiring for damage; rust in/on the reluctor; rust on the magnetic tip of the pole piece; rust raising the sensor off its seat; a broken/missing sensor hold-down screw ... see?

RUST is in that equation several times .... take good note!

 

[chem_man]

And, a decent code scanner will be able to read and show ABS OBDII codes.

 

[Mark156531]

Thank you for this help!! I'll probably come back with more questions later but you've given me a good place to start.

 

[Mark156531]

I just hooked up my code scanner and confirmed that you are correct. The scan indicates that a rear wheel speed sensor is failing. MyThinkcar scan tool is difficult to use but it does work.Thanks for leading me in the right direction.

 

[chem_man]

You are quite welcome.

 

[kanaikid619]

And, a decent code scanner will be able to read and show ABS OBDII codes.

I think I may be having this issue. Will the Torque Pro app be able to give me ABS/Wheel Sensor info?

 

[chem_man]

I am 90+% sure it will provided you have the Torque Pro app set up to access the extra GM PIDs. I see the entries for the ABS/Wheel sensors whenever I go in to add something to monitor (I do not monitor my ABS/Speed sensors myself).

Start the Torque Pro app, Click on the settings wheel in the lower left hand corner, then click on Settings that pops up in the new menu. Now, you should be seeing a long list of menu items beginning with General Preferences. Go down and select the one that says "Manage extra PIDs/Sensors". In the new screen that pops up, go to the upper right hand corner where the 3 vertical dots are and press the dots. Now from the new menu select "Add predefined set", and then select the "Pontiac/GM/Opel/Vauxhall" menu item and you should be set.

Now go into the monitoring part where you monitor the various sensors and add the ABS/Wheel Speed sensors you desire to monitor.

Good luck!