2006 K3500 ABS pulsing

[a5150nut]

2006 K3500 135091mi

Replaced Master cylinder 10/15 47025 mi
Replaced Hydro booster 1/21 105444 mi
No codes or lights
Lately on soft stops just as I'm letting up on brake the ABS pulses and feels like it might not stop. Once in a while it does this on harder stops.

I'm thinking maybe front wheel sensor. Feels like its front right but that's just gut feeling. Is there any way to test sensors?
Or to check ABS system without a fancy computer? My code reared sees nothing at this time.

[DmaxMaverick]

The ABSCM checks/tests the system constantly. Other than that, you need a fancy computer. If a wheel speed sensor was flaky enough to feel it, you should have a code and the ABS lamp would be on. A simple code reader won't show the code (need the fancy computer, or a $$ scanner/reader).

Sounds like a warped/sticky rotor. You can feel that, and it won't throw any codes. If the ABS is actually actuating (hear/feel the ABS pump pumping), you're gonna need that $$ scanner, or some time in a shop that services ABS.

[JohnC]

My Duramax did that. I recall there is a service bulletin on it. Problem was corrosion getting under the sensor mounting bracket and lifting the wheel sensor away from the tone ring.

[a5150nut]

My Duramax did that. I recall there is a service bulletin on it. Problem was corrosion getting under the sensor mounting bracket and lifting the wheel sensor away from the tone ring.

With the salt here in E Tennessee that could well be the problem. Gut tells me its right front. Get cataract surgery early tomorrow so I'll have to wait a while to check further. But it will still be in the back of my mind till fixed. . . . .

[JohnC]

No heavy lifting!

[spongebob]

rotor's are my guess

[a5150nut]

rotor's are my guess

no its the ABS pump pulsating

[a5150nut]

Ok today's update. Cataract surgery was a success now I will have to go to DMV to get glasses requirement removed from my license.

No for the brakes I changed to a new right front sensor yesterday still have the same problem. So today I took the take out from the right and replaced the left one with it. Still no joy.

There is a good shop not to far from me that is really good on electrical problems I will have to check tomorrow to see if they can handle it. They were Jeeps Only but have branched out to All Terrain. Was $150 before for a computer analysis.

Might have to wait to see whats happening with SSI and Brandon before I spend any $$$

[DmaxMaverick]

The diagnostic is only where the spending begins. You can replace the wheel hub for less than the $$ of the diag (you may be there in the end, anyway). A functional Bi-Di scanner is about double that (and some), and has other uses.

I picked up a Zurich ZR15S for less than $300 (HFT store discount, weekend sale, coupon, and a free bucket). It can run any module, and read/clear any active or historic codes from them. It can also run diagnostic and maintenance procedures, like ABS module tests and purge. It has Bluetooth and WiFi, updates the firmware on your PC, and a useful connected app. It's self-powered (AA batteries) and has a lighted connector plug (makes it easy to hit the connector buried under the dash on some cars). It isn't manufacturer specific and, so far, I'm impressed with it. Not made in China.

[DmaxMaverick]

HFT is having a sale right now, through Memorial Day. 25% off if you have a coupon. The scanners aren't excluded. Sorry, no free bucket this time. I can forward the coupon email to you, if interested.

[a5150nut]

Well its Thursday so I guess I missed the sale. The right rotor has a ruff pitted stripe 1/4 in wide on the outer inside face. I don't know if that might be causing the problem. Maybe replace the right front rotor and see. on a soft stop just as it gets to the stop point ABS pump pulsates and it pulls right. Kinda still waiting to see what the a$$ hats in DC do about the budget.

[DmaxMaverick]

Unless that rotor is causing the wheel to lock up, or slowing significantly more than the other(s), it should not cause ABS activation. If the ABS lamp is not coming on, the system thinks the condition, whatever it is, is normal, or not yet bad enough to sound the alarm. You really need to get a capable scanner in play to know if you're having an intermittent condition, that will set historical codes, but may not cause the ABS lamp. Many of the system errors must repeat within so much time or run cycles before actually showing you the lamp. If the condition is repeatable, repeat it, many times within the same run cycle. The ABS lamp should show up, if the condition is outside of the set parameters.

If the ABS pump is activating, AND it is pulling to the right, either the right wheel is locking up, or the problem is not the right wheel. Possibly, it could be a left wheel issue, and the (ABS) right wheel/brake is compensating, causing the R/H pull. An abnormal rotor wear could certainly be caused by this condition, as a symptom or result, and not necessarily the cause. Uneven rotor wear can also cause a braking bias (between the L/R), giving the ABS computer fits.

[a5150nut]

Ok leaving lunch today I stopped to enter roadway and the ABS light came on. Released brakes and re applied and it went out. My scanner has an ABS button so I checked when I returned home. I'm getting C0035 left front sensor. I replaced the right front and no change. So then I replaced left front with the one from the right side. Ordering another new sensor now and try it on the left.

[JohnC]

on a soft stop just as it gets to the stop point ABS pump pulsates and it pulls right.

That's exactly what the service bulletin addressed. Rust lifts the sensor away from the tone wheel and it falsely triggers the ABS. The brakes pull to the opposite side since that side is not being pulsed.

Make sure you clean the surface on the hub where the sensor mounts so it sits flush. I'm thinking the bulletin may have specified some sort of rust preventive, too,

[JohnC]

My Duramax did that. I recall there is a service bulletin on it. Problem was corrosion getting under the sensor mounting bracket and lifting the wheel sensor away from the tone ring.

Brakes - Bulletin No.: 02-05-25-008
https://www.tsbsearch.com/GMC/03-05-25-007D

[a5150nut]

Well received the new wheel speed sensor and got it in today. All is working properly now. But while working on it noticed the wheel bearing is starting to get loose. So next on the list to fix. . . .At least my brakes are working as they should.