Slow speed ABS activation fixed!

That's standard. I think it flashes 3 times? Maybe 4.

 

My memory is a bit fuzzy because of lack of sleep, but I think it was closer to 7.

 

Ok, I retract my original statement and say "maybe 3 + 4 times".

 

Well, I checked for codes again, and I got “PO504- Brake switch a/b correlation.” I have been checking for ABS codes and have not gotten any. This one came up when checking the normal systems.
I’m not sure if this could be related to the ABS issue. Anybody have insight on this?

I also am going to try mapping wheel speeds tomorrow. I have gotten readings from all of them but I’m pretty sure one or two is reading slower than the rest.

 

I'd get that occasionally when scanning an airbag code. Would only get an ABS light when scanning. I'd clear it and the light would go off as soon as I restarted the truck. Only thing I can think is I used to have a trailer brake booster installed and maybe I didn't get all of the harness for it out. My brakes work fine.

 

Have you inspected your brake lights to ensure they're actually working? I thought that was an indication of brake switch failure, where your brake lights may be going on/off unexpectedly. i.e. you step on the pedal, brakes go on, but then blink off, or shut off while pedal is still depressed.

 

I think you might be right about that code being for the switch. There were two codes I used to get and replacing the brake light switch got rid of one of them. My brake lights always worked fine though, I think it was something in regards to the two separate circuits in the switch not being in sync anymore, but I haven't finished my first cup of coffee yet either. I do remember I never had any real issues other than the code popping up when scanning an airbag code, and I swapped the switch to be proactive about it.

 

I haven't checked lately but I will. I had the code pop up a while ago and made sure my taillights were plugged in really well and it went away. But ya it sounds like that is not related to me ABS issue.
I did track my wheel speed sensors this morning and they are all reporting speeds but definitely not all in sync.

 

I’d start with the simple stuff.

Throw a brick on the brake pedal or wedge a board from seat to pedal close to full pressure. Then walk to the back and watch the brakes for any flickering or lights out.

If you tapped into the rear brake circuit for any reason (camper, trailer wiring, etc.), I’d review that wiring carefully especially if you or someone else used scotchloks/t-taps or similar wire-mutilating devices.

I’d be looking at the pedal, alignment with the plunger assembly, verify the plastic pad the plunger engages remains intact and isn’t cracked.

I suspect you may find something in those three which explain it, but it’s hard to say, not being there in person.

 

I'll check it out. I think previous owner had a topper brake light tapped into the taillight but should be new wiring since I replaced the taillight assemblies a couple months ago. Backup camera is tapped into the tow harness for constant accessory power. I'll double-check something did get sliced, and make sure everything is working correctly and then check the switch and pedal itself later this evening.

 

I took a quick look this evening and the brake lights and taillights all work fine. Blinkers and reverse lights too. I’ll have to look at the wiring and reverse switch more closely.
But when monitoring the speed sensors, I saw that I have one that doesn’t seem to be activating when the other 3 are.

 

I need to doublecheck if my MX+ will read the wheel speed sensors. If so, I need to build a dashboard for wheel speed. Their app lets me build various dashboards, I think I'm going to do one for fluid temps, one for fuel delivery data, one for air/fuel and ox exhaust sensor data, one for wheel speed, and basically go through with categorical dashboards in that way. Just sucks I haven't found a way to build dashboards outside the app then import them in. Building them on mobile is brutal.

 

Ya I’m using the mx+. It will read wheel speed and signal if/when ABS activates. I even changed the log and had it track wheel speeds which is the graph above. When it tracked the ABS activation, it looked like all but one activated at some point while driving.

 

I think I finally got my ABS issue fixed. I re-adjusted the wheel sensors I messed with and did the zero-point calibration. Then I made some rear brake adjustments. The adjuster screws on the backing plates had a lot of space and the parking brake wasn’t adjusted well. Fixed all those things and my issues seems to be gone. Fingers crossed!

 

How's this holding up? My slow speed activation is back after over a year. Super fucking annoying as it seems to be worse than before. Tried doing the Zero-point a few times and can't seem to get it to work after dissconnecting the battery before each try. Using pins 4 and 12 on the OBD (pretty sure those are correct according to the video).
Gonna try and clean the shit out of the sensors and rings again this afternoon then see if things get better, then add another part of troubleshooting as to isolate things a little. May try the things you tackled, adjusting rears etc to see if that plays into anything. Though I believe they are adjusted, cranks move and slack in cable is non-existant.

 

Mine has mostly stayed gone. I have had it happen a couple times in the last however many months but my guess is that it’s from pulling on the sensor wire. I’ve been turning sharply and had a wheel drop from a hole in the ground or something. I remember I cleaned out the sensor and tone ring with q-tips and a little brake fluid. Then I reseated it very carefully (took a try or two). Then I did the zero point calibration. That finally did it for me. Good luck.
I think I have a spare sensor off a wrecked truck depending on what side you’re having trouble with.

 

Yeah I'm having zero fucking luck with the ZPC this go round. Did you use pins 4 and 12? When I touch them the abs light will blink but it's not giving the long beep like instructions say it will.
Driver's side I believe is where my problems are but when I did a resistance check in the sensors the first time I fixed this they were the same.

 

Just in case (because I made this mistake the first time) the OBD pin position is upside down from the picture.
Let me look and see what side sensor harness I have. If it will work I’ll send it to you and you can see if it’s a sensor issue or if there’s another issue.
Other option is you can get an OBD that reads ABS codes and monitor those to see which is dropping out.

 

Try pin 4 and 13 instead.

 

I knew i.saw that somewhere. But didn't remember finding it last time I got it to work, it was recently. Gonna try this evening.

You mean a BT OBD scanner or the more expensive ones? I have a veepeek I wasn't aware any of the little ones could do that.

 

Not sure which one you have, but I think you can get OBD Fusion and it should connect to advanced diagnostics. Sadly you have to pay for them. You'll have to double-check if your reader will work with those.
I have the OBD MX+ and I was able to monitor my ABS sensors to see when one was dropping out. It took some time and learning to get it figured out. Hopefully the third time is the charm and it will work for you this time.