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Discussion Starter #1
2008 Colorado 4x4
I replaced the rotors and pads; Raybestos Premium parts.
As we know on the 4x4 Colorado, the hub needs to be removed, and upper ball joint needs to be undone via the 3 nuts at the control arm, in order to remove the rotor. (Why can't the rotor be designed onto the outside of the hub?!)

Anyway, the sensor ring got somewhat distorted during the hub removal process; I straightened the ring flange on the anvil using a broad drift and a hammer. After cleaning up up the rust and corrosion I put the sensor ring back on the hub.

I used anti sieze everywhere on the hub that made sense to get it apart next time. It all went back together just fine.

On the road test the ABS FAULT and ABS light came on, and stayed on. I shut the motor off and restarted a number of times. I tried to reset the computer using the unhook the battery/ignition switch method. No go.
My code scanner gave me 6 codes. The first 2 being the sensor both Driver side, and Passenger side. 2 indicated voltage concerns both sides, and I can't remember the other 2 codes.
I am going to do the resistance test on the sensors (does 50 ohms sound right?), and the voltage test at the sensor connector. What voltage am I looking for? I don't have a shop manual.

I have completed writing my book. Can you help me with more info? Thanks
 

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Perhaps someone can give you the numbers for the sensor testing but they are probably dead on arrival . I don't see how they could have survived the disassembly process . I'm curious about the 3 nuts at the control arm to remove the hub . On my truck the hub is bolted to the knuckle by 4 bolts . As to the hub and rotor being a " CAPTURED " design it's really a clever thing . It moves the contact area of the rotor further away from the hub to let the rotor cool better reducing warpage .
 

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Discussion Starter #3
Perhaps someone can give you the numbers for the sensor testing but they are probably dead on arrival . I don't see how they could have survived the disassembly process . I'm curious about the 3 nuts at the control arm to remove the hub . On my truck the hub is bolted to the knuckle by 4 bolts . As to the hub and rotor being a " CAPTURED " design it's really a clever thing . It moves the contact area of the rotor further away from the hub to let the rotor cool better reducing warpage .
I would like to do the ohms and voltage tests on the sensors before I decide to undertake that bloated disassembly process again just to replace them. The 'Captured' design sounds great, less heat, less warpage, but I have to plead that there must be a way to capture it with the rotor on the outside!... Especially if the sensors are likely to be damaged each time the brakes are done (unless someone has an on board brake lathe so the rotors can just stay on).
What I have been seeing in pictures is the 2 wheel drives use the 4 studs on the upper BJ to control arm, and the 4x4 uses the 3 studs (hopefully larger size studs). Is yours a 2 wheel drive?
I will post my results regarding the sensor tests. I am wondering what the sensor air gap should be? The gap could get inadvertently changed upon installation because of the overstuffed fit of the sensor ring and wire in the hub opening of the knuckle, and having to work against the drive axle pushing outwards while getting the 4 hub bolts to hold it in place. The design sucks but that's my opinion:) Thanks
 

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Why did you replace the rotors ? Did you neglect to check pad wear and let them tear up the rotors ? The whole principle about preventing rotor warpage was replace pads before that happens and you wont have to pull the hubs which usually ends up in damaged sensors . While I'm not 100% certain the sensors are magnetic not an air gap type . That is why they did not survive the disassembly and anvil . If you check out this 3 part video it will definitely shed some light on this subject and you will see what I mean about the 4 hub bolts on my 2008 4X4 Z71 . Sorry , but best option I see for you is pulling the hubs and just replacing the sensor rings. I hope you can prove me wrong . Search youtube for , bursott1 / hub replacement , for video.
 

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Discussion Starter #5
Why did you replace the rotors ? Did you neglect to check pad wear and let them tear up the rotors ? The whole principle about preventing rotor warpage was replace pads before that happens and you wont have to pull the hubs which usually ends up in damaged sensors . While I'm not 100% certain the sensors are magnetic not an air gap type . That is why they did not survive the disassembly and anvil . If you check out this 3 part video it will definitely shed some light on this subject and you will see what I mean about the 4 hub bolts on my 2008 4X4 Z71 . Sorry , but best option I see for you is pulling the hubs and just replacing the sensor rings. I hope you can prove me wrong . Search youtube for , bursott1 / hub replacement , for video.
A couple of the pads were worn down unevenly to 1/8" on one end, 1/4 at the other. They were cocked and bound in the calipers. I had to knock a couple of them out.
The rotors had grooves and ridges, and needed replacing. I didn't want to do a pad slam but will consider it next time🤓
I was wondering if I should have installed ceramic pads in there (instead of semi-metallic) to be easier on the rotors which might not require replacement next time or two?
I saw images on YouTube showing the 4 bolt setup, and the 3 bolt setup. I think I might have watched a 3 part video on YouTube already but thanks I will check that out.
I am afraid you are going to be proven right about the sensor rings but at least I am good at pulling the hubs now, and there won't be rust n corrosion to deal with. The antisieze I used will have that stuff slide apart like greased lightning⚡
Thanks for your insight.
 

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Discussion Starter #6
Why did you replace the rotors ? Did you neglect to check pad wear and let them tear up the rotors ? The whole principle about preventing rotor warpage was replace pads before that happens and you wont have to pull the hubs which usually ends up in damaged sensors . While I'm not 100% certain the sensors are magnetic not an air gap type . That is why they did not survive the disassembly and anvil . If you check out this 3 part video it will definitely shed some light on this subject and you will see what I mean about the 4 hub bolts on my 2008 4X4 Z71 . Sorry , but best option I see for you is pulling the hubs and just replacing the sensor rings. I hope you can prove me wrong . Search youtube for , bursott1 / hub replacement , for video.
That's right, I had already watched bursott1's removal and installation series of 4 or five vids. One thing I did differently was use a screw driver to lock the rotor to the caliper (through a hole on the caliper, and the cooling fins of the rotor) to loosen and retorque the 6 rotor bolts and the axle nut.
I watched a lot of other YouTube vids too but couldn't find a torque that seems right to me, for the caliper pin bolts; 59 lb ft/lb plus 30 to 45 degrees rotation seems like a lot for a bolt that size. Do you know that torque value; What do you use; Apparently its a 'stretch bolt'.
I will list all the torques I used for this job.
I think I misunderstood you regarding the 4 bolts thing. I thought you meant the upper ball joint studs, which I have seen as 3 and 4 bolt design. All the hub to knuckle setups I've seen on the Colorados have been 4 bolts, yes.
 

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Discussion Starter #7 (Edited)
Watch "How to Test an ABS Wheel Sensor" on YouTube
There are a number of YouTube videos about testing wheel sensors.
A known good sensor is useful to compare voltage output and resistance values to.

There are 2 kinds of wheel sensors that OldTime alluded to a ways back.
ScannerDan describes a lot in this video but he lays a lot on fast which can be confusing.
Watch "Magneto Resistive ABS Wheel Speed Sensor Test - 2006 GM" on YouTube
 

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I find your in-depth research into this fascinating. I wish I had your passion . Good stuff !!
I have some torque values for you .
Caliper guide pins 29
Caliper bracket bolts 129
Hub/Bearing assembly to rotor bolts 88
Hub/Bearing assembly to knuckle 92
Hub axle nut 191
ALL ARE FOOT POUNDS . From Chiltons repair manual .
I just remembered another way I used to check sensors . I used to work at a dealership were a friend of mine from school is the parts manager . He would grab a bearing assembly out of stock an let me measure the ohms so I could compare it with the suspect bearing off my truck or car. Worked real well until new ownership gave us the stink eye on such things . But I see no reason a person couldn't try this at a Pull A Part yard . Ironic that both my ABS sensors failed before I needed new pads.
 

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Discussion Starter #9
I find your in-depth research into this fascinating. I wish I had your passion . Good stuff !!
I have some torque values for you .
Caliper guide pins 29
Caliper bracket bolts 129
Hub/Bearing assembly to rotor bolts 88
Hub/Bearing assembly to knuckle 92
Hub axle nut 191
ALL ARE FOOT POUNDS . From Chiltons repair manual .
I just remembered another way I used to check sensors . I used to work at a dealership were a friend of mine from school is the parts manager . He would grab a bearing assembly out of stock an let me measure the ohms so I could compare it with the suspect bearing off my truck or car. Worked real well until new ownership gave us the stink eye on such things . But I see no reason a person couldn't try this at a Pull A Part yard . Ironic that both my ABS sensors failed before I needed new pads.
Excellent!
I used all those values except for the caliper pins I went 30 fp + 90 degrees. I didn't even like the feel of that but some on another thread said it is 59 fp + 30-45 degrees. That sounds like too much for those wee pins eh?
I went 35 fp on the 3 upper ball joint stud/nuts. I just looked up the general torque for a 3/8" grade 8.
 

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Discussion Starter #10
I guess some is passion but I don't know what fraction is stubbornness or OCD🌞

I can order a sensor from the auto parts store to check the resistance. I can return it for a re$tock chg as long as not installed.

There must be a simpler explanation of how to test the new style sensors, than what scannerDan gives in the above YouTube vid.
I'm just getting the parts together now, and will get into this tomorrow.
I'll let you know.
Thanks a ton.
 

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Excellent!
I used all those values except for the caliper pins I went 30 fp + 90 degrees. I didn't even like the feel of that but some on another thread said it is 59 fp + 30-45 degrees. That sounds like too much for those wee pins eh?
I went 35 fp on the 3 upper ball joint stud/nuts. I just looked up the general torque for a 3/8" grade 8.
Right on the money for the torque value of the upper ball joint . (y)
 

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Discussion Starter #12
I checked the resistance value of the first of the 2 replacement sensors. It read 456K ohms. I checked the original sensors and both indicated open circuits. I don't have the actual specs for it but Eric The Car Guy of South Main YouTube channel said the values should be in the Mega ohms range. I was satisfied enough to go ahead with the swap but when I ohms checked the 2nd of the new units it showed an open circuit like the originals!! 😲
I called the auto parts store and said I must have a defective new unit. They are rounding up another one for me for this AM. I hope and pray this 3rd new unit reads Mega ohms like the first one. I am getting real good at pulling these hubs but my confidence is waivering😕
Does anybody have the ohms specs for these wheel sensors?
 

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You might get lucky and get the ohms values , but if you don't try this before you put it all back together .Lay the assembled hubs / sensors in the knuckle or close enough to plug them back into their connectors . Then turn the ignition to run and the codes should disappear . That way you can be confident everything is as it should be before you tackle the reassembly . Then have a cold one , you deserve it for all you put into this .
 

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Discussion Starter #14
GM knew/knows this ring sensor was a poor design. They discontinued it 1 year later, in 2009. They went to the standard post style with the single screw mount; It can be serviced from behind without removing the hub. 👍🌞👏😊
Thanks again for your help OldTime.
 
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