02 Buick Rendezvous 147k ABS Issue (NOT your typical problem) please help!!!!!!!!!!!!

[greatcars]

Hey everyone, new to the forum so thanks for any help you may be able to provide. I know all about the typical abs/AWD disable light, the wires to the sensors being to short and all that jazz. This is NOT that issues. All wires have been checked and are fine and I do not get the AWD/Disable light. There are no codes stored in the Electronic Brake Control Module and all speed sensors are giving accurate readings (within 1 mph).

Both front hub assemblies with speed sensors have been replaced within the last 10k miles.

The issue that I'm having is that when coming to a stop the ABS will engage, not every time, and not specific to any event (i.e. turning the wheel when stopping, slamming on the brakes, etc.) The only common trait when it occurs is the vehicle is less than 10 mph. It never engages at highway speeds or anything else. I have an Autel Maxidas DS708 scan tool and have hooked it up and am getting nothing out of the ordinary. It does show that the abs is engaging when the problem happens but it's not giving me any indication of why and all other parameters are showing normal.

Any Ideas??? If your familiar with my scan tool and have any suggestions on tests or things I should be looking it would be helpful as well, I just bought the scan tool a couple weeks ago so I'm not an expert with it by any means.

I've read about the flow valve in the rear transfer case but I don't believe that is the issue because everything I have read says that the AWD/Disable light will come on and you will get codes from that being clogged.

I've also checked the connections under the car by the drivers seat, pulled them apart and looked for corrosion. There was no corrosion and I put some dielectric grease on them and put it back together, still getting the issue.

 

[lrj975]

how did you check the wires and conclude they are fine?

This sounds like typical slow breakdown of the wheel speed sensor wires at the hub, both left and right fronts are suspect. The wires can deteriorate from the inside and from visual inspection still looks normal from the outside, but causes intermittent signal loss, until they finally just break, may take a couple weeks/months at that point, inevitable. ABS is correctly doing what is is told to based on faulty inputs.

Try to splice in new wires for a 99cent fix or get Dorman #970040 same for left and right.

A C0035 etc isnt tossed unless there is no signal from wss at startup, or afterwards a loss of signal for like 10 seconds, try starting car with a speed sensor connector unplugged to see that.

 

[greatcars]

how did you check the wires and conclude they are fine?

This sounds like typical slow breakdown of the wheel speed sensor wires at the hub, both left and right fronts are suspect. The wires can deteriorate from the inside and from visual inspection still looks normal from the outside, but causes intermittent signal loss, until they finally just break, may take a couple weeks/months at that point, inevitable. ABS is correctly doing what is is told to based on faulty inputs.

Try to splice in new wires for a 99cent fix or get Dorman #970040 same for left and right.

A C0035 etc isnt tossed unless there is no signal from wss at startup, or afterwards a loss of signal for like 10 seconds, try starting car with a speed sensor connector unplugged to see that.

Well I know it's not the wires because both front assemblies have been replaced within the last 10k miles. Aside from that I also visually inspected them for any breaks, I do have a power probe set that I just purchased and can use to definitively ensure that the wires are good, but I experienced the typical problems for a good 3 months prior to replacing both front hub assemblies. This acts completely different. When the wires were going bad before the abs would engage even at highway speeds when hitting the brakes and would almost always disable the AWD. Now it only occurs right before the vehicle comes to a complete stop. I did some other research and found that the connections between the Electronic Brake Control Module and the BVM can sometimes get corrosion and cause the intermittent abs engagement without causing the AWD/Disable light to come on. I think that will be my next test.

 

[lrj975]

Well I know it's not the wires because both front assemblies have been replaced within the last 10k miles.

well ok but that's different, the wire that breaks is from the wss connector to the harness, not the wire from the connector that's attached on the hub. As this wire deteriorates over time it starts out with ABS kicks in at low speed, next AWD Disabled backing out of driveway, then AWD Disabled as soon as car is started. That Maxidas DS708 ought be able to read obdii chassis codes so start the car with the wss disconnected and will get a c0035 to confirm.

 

[quinny]

Has anyone had any luck solving this problem?

My elderly parents have just handed me a stack of bills by mechanics saying they will fix this...new hubs, rotors, harnesses, and i believe more.

its not fixed. They have poured money into this 04 awd ultra. One problem after another. Bought new at key Buick in Jacksonville Fl.

 

[lrj975]

@quinny this gets fixed all the time with proper diagnosis and replacing faulty parts, suggest starting new thread so stories don't mush together, with your situation, clear description, symptoms, how long occurring, what was checked, what mechanic says, your DIY skills etc.