NEED HELP Weird issues

[Stuntmanmike1977]

Hello everyone. I'm having an issue with the brake system. The pads I put on started to squeal really bad as it got colder probably will replace them. Anyway sounds like there is a motor running (not the one under the hood) while driving and at a stoplight but not all the time. ABS light comes on and off intermittently and the ABS kicks in sometimes when it's dry outside. On top of all that the third brake light started working again after almost 4 years of being dead! Any ideas what could be causing this chaos?

 

[freddyboy61]

The first thing you're going to have to do is provide the vehicle information (year, model, engine, trim level).

 

[Stuntmanmike1977]

Oh, sorry. 2003 trailblazer LTZ swb

 

[mrrsm]

If you can feel a Vibration coming through your Brake Pedal... it might be an issue with one or both of the Brake Hub A/C Coil Pick Ups moving TOO far away from the Teeth of the Reluctor Wheels inside the Front Hubs due to "Rust Jacking". Ordinarily, the Rotation of the Wheels at all times provides the means to generate a Mild A/C Current of around 450 mV (Milli Volts) that confirms with the PCM that you have NOT accidentally LOCKED UP YOUR FRONT WHEELS on either a Slippery or upon Icy Surfaces.

Once the Front Wheels STOP Rotating... they can NO LONGER BE EFFECTIVE IN STEERING THE VEHICLE... and the Vehicle will continue to move in the last direction of guidance (vector of SUV's momentum) just before the Wheels Locked Up. The ABS Unit and the PCM will do everything possible to interpret a Low Speed Failure of Rotation to activate the ABS Unit and keep the wheels rolling.

The ABS Unit is designed to provide you with the means to Rapidly Apply and Release the Brakes in contact between the Pads and the Rotors in such a manner as to Prevent Locking Up The Wheels. This Video shows How to Diagnose this Problem on GMT360 Vehicles and How to perform a Repair (with the Alternative Action being to REPLACE BOTH FRONT WHEEL HUBS) :

There are a LOT of Good Clues covered in this Video that may alert you to something that requires a Second Look to figure out exactly what has gone sideways with the Braking System:

 

[Stuntmanmike1977]

I'll try cleaning them up then report back. Thank you.

 

[mrrsm]

:>)

 

[Stuntmanmike1977]

Hello everyone. Haven't got around to it yet, New England weather sucks. Anyway, I know it was being discussed already but just wanted to post the codes I got off my scanner. All 3 are the ABS system. I know I need to check the connections just thought it could be something else. Also the driver side wheel bearing and hub assembly was replaced this past summer.

 

[Mike of Maine]

Its a chilly one this morning! Brrrrr!!!
I have been following here, just wondering if your scanner has datalogging? I had almost identical weirdness that I couldn't find with any visual inspection. Throwing me into ABS in a dry, from a gentle stop in my driveway, also dropping acceleration because it sensed traction loss, triggering anti-slip/throttle just died on acceleration. (fun at the rotary!)
When I looked at the scanner log, my right front hub had a 2 mph variance but only to around 5mph and then appeared to work as expected.
I think my issue was similar to what mrrsm was describing.
Just like he said, rust built up on mounting surface where the speed sensor goes in the hub can be all it takes to throw a fault code.
I haven't had to do these repairs personally but seem like good places to look...
It seems the EBCM ground under the drivers seat on the frame that could be responsible for these issues. New England rust to go with the weather!
You may want to double check your contacts at the ABS module plugs for corrosion as well.

 

[mrrsm]

There might be actual physical damage to the Front Wheel Speed Sensor(s) AND the VSS Harness(es) with any Upper "A" Frame Contact Abrasions, Cuts or Breaks in the Black Wires that look similar to THESE and thus, calls for a very close re-inspection along the entire lengths of them ALL:




Please take the time to investigate Post#65 in THIS Thread for the Diagnostic Training involved with using the BEST Diagnostic Tool for investigating ABS Wheel Speed Sensor Issues:

How To Use PICO #2204A & HANTEK #1008C Oscilloscopes

From time to time… it will be handy to be able to switch your 4mm Banana Plug Leads either to....or from...your Oscilloscope and over to your DMM… (or...Vice-Versa) ...and having these Very Inexpensive Adapters on hand will turn out to be a very good idea: BNC TO 4mm BANANA PLUGS ADAPTERS...

gmtnation.com

Eric "O" from SMA (South Main Auto) also has a version that will appeal to GM and GMC Late Model Vehicle Owners that sport the Digital Square Wave Sensors vs. the Original A/C Generator Style versions on the GMT360 Vehicles:

 

[Stuntmanmike1977]

Strange thing is I cleared the codes and the ABS light hasn't come back on yet, been about 5 days now but still gonna check it out today. Another issue has arised with the brake lights. For some reason the fuse was out number 34 I believe. Anyway, I replaced it with a new one and now when I hit the brake the chmsl still doesn't come on and I do have power to the light itself and now the driver side blinker light comes on and flashes really fast while I'm braking then goes back to normal when I let off the pedal! Never heard of this, any thoughts?

 

[Mooseman]

Check the wires/grounds and bulbs at the taillights. A possibility a filament inside a bulb has shorted. A possibility is broken wires inside the liftgate rubber boot shorting or open.

 

[mrrsm]

And check out Post #5 in @Realism 's Epic Thread on "Grounds"....in Post #5 in particular. The Driver's Side Left Turn Signal, The Left Headlamp and The Fuel Pump Relay all share a Common Ground as illustrated below at the Position G-107 on the Lower Center Driver's Side of the Engine Block. If that ground is *sketchy* and the driver is performing a Left Hand Turn. the High Electrical Resistance experienced by ALL THREE simultaneously can cause the Headlamps to Flicker and the Fuel Pump Relay to Kick OFF and Stall the Engine:

 

[Stuntmanmike1977]

Problem solved well, one of them. Turns out the brake light / turn signal issue was due to a bad circuit board in the driver side tail light. Still no third brake light but, at least I have the other two. Will probably have to replace it. Have power going to it so it's probably wore out. Thanks for all the helpful info as always.

 

[mrrsm]

This R&R Video show hoes to gain access to the places that might "Work Harden" and break Hidden Harness Wires that can Short Out...or simply have a Burned Out Sealed Light Unit as Well:

 

[Stuntmanmike1977]

Yeah, pretty sure it's the light itself cause if you smack the heck out of it it lights, fades then goes out. It's fully lighting at the moment. Question is any way to use a heat gun to loosen the black adhesive and pull the lens cover off to possibly find a loose connection? Or do I need to get a new one

 

[mrrsm]

Maybe it's just me... But for Twenty-Five Bucks from THIS eBay Vendor... seems like just getting a Brand New Third Light Assembly is the easiest thing to do to solve the problem:

For 2002-2009 Trailblazer Envoy GMC 15201921 LED Third 3rd Brake Light Tail Lamp | eBay

Third 3rd Brake Light Lamp High Mount For 02-09 Chevrolet Trailblazer GMC Envoy. 2002-09 Chevrolet Trailblazer Center High Mount Third Brake Light. 2002-06 Chevrolet Trailblazer EXT Center High Mount Third Brake Light.

www.ebay.com