abs fault

Tag 43

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#1
Make
chevy
Model
colorado
Year
2007
Miles
over 200,000
Engine
5 cyl
I have a 2007 chevy colorado Z71 4x4 over 200,000 miles. the abs light is on when i start the truck. if i back up it will go out but, come back on when i put it in drive and start driving. i have changed both wheel sensors. it still does the same thing. when the light is out the brakes will chatter, when the light is lite everything works fine.
 

nickb2

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#3
If, you have a chassis code puller, would really help here. Plz post that.

If you have erratic sensor codes, swapping just the sensor/s will do nothing if reluctor is shot.

It is normal when abs light is on to have no pulsating at wheel brake, abs module has effectively just gone in a form of limp in mode, which is just like removing the fuse. This indicates good function of the ABS unit.

Honestly, if you can't pull the codes from the ABS/chassis modules, I don't know where to start with helping you. I can provide all the wiring's, every flow chart I have in my arsenal, you might be chasing something that a bore-scope could see.

To pull chassis codes, you will require a different code puller than your down cheap walmart thing. They actually do have one, but it is close to 200something dollars, you could do way better by buying some sort of tech 2 clone off amazone or aliblabla.
 
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nickb2

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#5
I am probably sounding arrogant, but really, I am not. You probably paid the price of this scanner in useless parts you threw at it. There are many viable options out there to get live data from the wheels and also dump valve etc in abs unit.

Here is a good deal, tech 2 clone with vci for reprogramming, will probably pay for itself in a few repairs if you plan on keeping the truck.
http://www.obdexpress.co.uk/wholesale/gm-tech2-gm-diagnostic-scanner-32mb-card-tis2000.html

If you don't plan of keeping this truck, then go more global and check out some sort of laptop software and elm based bidirectional options., just google that, it should provide a great variety of options of what to buy for your toolbox.
 
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#6
https://www.rockauto.com/info/314/19121727_Primary__ra_p.jpg

Is your Mickey ABS control unit as made law by our stupid congress paying a Standford theoretical professor playing games on his computer stating ABS is 14% safer than not having it. ABS has been law for all US vehicles.

Rear brakes should only have around 20% of the braking power as the front to keep from spinning out, on other GM ABS vehicles, using the valves in the ABS to pulse rear full size brakes, rather than using equalizers or smaller brakes. Sounds like yours is this way. This is a danger.

For this POS ABS unit also need a scanner to bleed your brakes and the manual states don't run that ABS pump more than a few seconds or you will burn up that POS motor. Not up to date, got sick of GM, government had to bail them out, but used to need a GM scanner with an ABS module at some ridiculously high price. Should have four wheel sensors, how did you determine which ones were bad. Most have connector near the brakes and are exposed to road salt. I just cut those connectors off and solder the wires with water proof heat shrink. Most are just a few turns of #40 AWG magnet wire wrapped around a nail like permanent magnet. Ohmmeter should show a low resistance continuity.

Module itself is around 500 bucks and definitely a throwaway piece of crap. And if you need to replace it, it will be loaded with air so should have a scanner to turn it on, but only run it for a few seconds or you will burn up your module. This is really a bad joke.

Good optional ABS would pulse at 10 times per second, this piece of crap is more like one pulse per second, also used for traction control, another bad joke.

Don't brother writing your congressman, don't know crap about vehicles.
 
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#8
Until the early 70's, automotive manufacturers were designing their vehicles, then the NHTSA, EPA, and DOT took over. EPA is in charge of emissions and tests fuel economy, DOT states how bodies should be assembled, NHTSA was equipment must be install. Ha, no problem for an engineer to deal with a bean counter, these governmental have the final say on how an automobile is put together.

Really not much difference between a Cadillac, Lexus, or a cheap Cruze, body is practically the same on all passenger vehicles for the unibody. Also unrepairalbe in a so-called accident, to the wrecking yard it goes, all those many panels are welded together.

NHTSA says you will have ABS, even though they are pure crap pulsing once per second, if your vehicle slides on a ice spot than hits a bare spot, your front end can fall apart.

Really no longer the land of the free.

For years generic scanners would not touch ABS codes, claimed they didn't want the liability even though ABS insisted would not affect the primary braking in vehicles. But okay for anybody to purchase and install components for the primary braking system. Crazy!!!

See now some generic scanners to read the codes, would cost around 5,000 bucks for a GM scanner, bit too much for the average owner.

And ABS does affect the primary braking system, if a solenoid valve stays closed due to gummy fluid, no brakes to that wheel period. These congress demanded ABS really are examples of made in China Crap. Those valves are tiny and poorly made.
 

Tag 43

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#9
If, you have a chassis code puller, would really help here. Plz post that.

If you have erratic sensor codes, swapping just the sensor/s will do nothing if reluctor is shot.

It is normal when abs light is on to have no pulsating at wheel brake, abs module has effectively just gone in a form of limp in mode, which is just like removing the fuse. This indicates good function of the ABS unit.

Honestly, if you can't pull the codes from the ABS/chassis modules, I don't know where to start with helping you. I can provide all the wiring's, every flow chart I have in my arsenal, you might be chasing something that a bore-scope could see.

To pull chassis codes, you will require a different code puller than your down cheap walmart thing. They actually do have one, but it is close to 200something dollars, you could do way better by buying some sort of tech 2 clone off amazone or aliblabla.
I was taking a guess it was the wheel sensors that was bad. I have not pulled any codes. is this reluctor ring part of the bearing hub ? can it be replaced? or do I have to replace the whole bearing hub? if that is the case can the new sensors I just put on be taken off with out breaking them? I am sorry for so many questions all at the same time. I know some one that has a reader that I think will work on my truck. it may take a couple of days to get the codes. thank you for all your help.
 
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#10
1992 Deville had the ABS sensors as part of the hub bearings, that was a major job in trying to remove those darn things with ten years of road salt. Also very expensive replacing the hub bearing because of a tiny hidden broken wire inside.

rockauto.com shows photos of what you have:

https://www.rockauto.com/en/catalog...brake+&+wheel+hub,abs+wheel+speed+sensor,1912

The easy kind, most are two wire, meaning just a coil of wire around a magnetic pole, an ohmmeter ten bucks at most places now can to a continuity test, usually low value of ohms as opposed to a completely open circuit. Cables are part of the assembly and are short with connectors to the vehicle harness, those connectors get corroded losing continuity.

Most of the ABS codes deal with opened or shorted wheel sensors, power on relay or ABS pump relay. Again an 89 cent microcontroller is used, if that is bad have to lay out 500 bucks for a new module.
 

nickb2

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#11
I am sorry for so many questions all at the same time.
Plz don't be sorry.:confused:

The more questions you ask, the more we are informed on how to help you.

On your model, the reluctor is in effect in the hub itself. No way around it, you have to replace the whole bearing unit.

But plz, do your self a favor before going mac guyver again:p, try to get those codes. That would be a huge time saver, not to mention :money: saver.

That way, I will provide the proper flow chart.

SO, as usual, I will provide cheap china links that will ONLY read ABS codes. They have no bi directional functionality, unless you upgrade to superior elm327 dongle/interfaces and proprietary software.

SO my advice, on a budget, buy something like this, slap that app on phone, bingo, you get codes and MAYBE (probably not) some live data.

Ok so this is a review, so if you have time and watch it. It gives an idea what it does.

 

nickb2

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#13
Of note, even though it says it works only with win 7 and 8, don't worry, a virtual machine takes care of that.

I can talk you through that if ever you try this option to be a better DIYer. ;)

This is mostly a learning site, unless I post whilst impaired and then forget ppl don't like french videos, then I guess it tit for tat.

But right now, I can provide full wiring for your truck, but none of that will help if you can't access the brain if there is some sort of internal short. This after all, a 2007 colorado. Not a big seller up here. So I don't have any fast easy fix, cuz I see 1 or 2 a year.
 

nickb2

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#14
But I can give you a trick that may help. Remove the sensors you just installed, they should not be hard to remove. Then, use shop air and rotate wheel a full two turns. Install sensors, go drive truck. If abs light goes out for good, dirty reluctors. :fixed::D
 

nickb2

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#15
Sometimes, when a bearing goes bad, or a seal goes bad, crap tends to fill the slot of the reluctor. What happens then, pulsating braking, the car sends a signal that it is in slip mode, applies abs, shuts down pump/circuit when it realizes it is just getting a false erratic sensor signal. Which is exactly what you are describing as a symptom.

This is why I mentioned a borescope. ;) But not everybody has one of those handy. So a hail mary is shoot the living daylights out of those slots. May help. When I say shop air, I mean 120psi, not a bicycle pump.