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Discussion Starter · #1 ·
I have not been around here for many years and when I was I usually went to Coloradofans. Any way, I now have a long standing problem that is getting worse and In an area where I have never worked.

I have a 2005 Z71 2wd Colorado with a 3.5. For many years it had a highly intermittent ABS sensor problem. Initially it only occurred when it was 85 to 90 degrees outside, or If I was towing a heavy load and lots stopping. There were never any codes stored but I would get ABS lights and traction faults. Over the years the failure temperature gradually lowered and now I am getting them with temps below freezing and not hauling a load.

I need to use the truck with 2 axle trailer for several trips of 200 miles or so, and my daughter will be driving it, not me. So it is time to fix it. Today I and another Colorado owner jacked up the truck looking for obvious problems with the front wheel sensors, brakes, and tires. I did find some accumulated flakey rust inside the mounting ring that contains the front sensors. Without logging errors we do not know which one is causing the problems. We cleaned out all of the accumulated rust in that area and cleaned the face of the magnetic wheels that rotate in front of the sensors. I thought this might take care of it.

I got 2.5 miles down the road and I had the problem on a cold truck with outside temps at around 28 degrees. I went back to my friend's unheated pole barn and we looked at again. Hubs and bearings and tires are fine. So I really do not want to pull the hubs just to replace both sensors. I have a new pair of sensors that I could install but can not figure out how to replace them without pulling the spindles / hubs. The reason we are leary of pulling the hubs is my friend did to his at around 250 K miles. They were impossible to get out . He had to use a 4 ton porta power to get them out. We went to borrow that porta power again and it is broken. I do not have a source for another one with buying one.

So now my question. Is it possible to get those sensors out without pulling the hubs first? If so, how is it done? This is a 2WD Z71 and uses the same parts as a 4WD Colorado except for no front drive shafts and CVJs. It has torsion bar front suspension.

Any thoughts or ideas would be greatly appreciated.
 

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The odds of removing and replacing that sensor without pulling the hub is darn near impossible. IMO the best solution is to replace the hub with one that has the sensor already in place as one complete unit. You have an 18 year old truck that you do towing with, new hubs seem like a wise move to make. It's not a complex job, just need some patience, and there are tons of video to help walk you through the process. Try to get the truck scanned with a tool that is able to read ABS faults, they may still be stored, or wait till you get the dash light warning again to try pinpointing which one, or both, is bad.
 

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Discussion Starter · #4 ·
I'm just guessing here. My truck is a 2011. I think the hub(s) will have to come off. There are some pics here of the sensor installation on the hub: How To: Front Hub/Wheel Bearing Replacement
You guys are not telling me what I want to hear, but you are probably right.

SO what I think I am going to try first is to determine which side it causing the problem. A different friend that owned and ran a foreign car repair shop for 38 years retired and sold out everything. So I I no longer have access to his Tech 2 scanner. We tried on two different occasions in the past to pull an ABS code and there were none. Now I will try to get or buy a scanner and determine which side is causing the problem. I can now get it to fail by letting it idle and heat up enough to get an error in 15 to 30 minutes without moving the truck. My thinking is with the truck cold I will get a hair drier and warm up the sender and cable connections on one side and then the other to see if I can determinne the side and cause of the error.

I received two sendors on Sunday from Amazon (they are cheap). I now have new spares. Once the side is determined, I intend to fashion a puller to catch the lip of the old one and see if I can pull it off in place. They just press on the hub and need a .005 or .006 clearance on reinstallation which is also one thing I have not checked on the existing ones.

If I am not successful I will follow your recommendations and install a new hub, or maybe two, with new senders.

Thank you for the input. I will let you know what fixes it.
 

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You guys are not telling me what I want to hear, but you are probably right.

SO what I think I am going to try first is to determine which side it causing the problem. A different friend that owned and ran a foreign car repair shop for 38 years retired and sold out everything. So I I no longer have access to his Tech 2 scanner. We tried on two different occasions in the past to pull an ABS code and there were none. Now I will try to get or buy a scanner and determine which side is causing the problem. I can now get it to fail by letting it idle and heat up enough to get an error in 15 to 30 minutes without moving the truck. My thinking is with the truck cold I will get a hair drier and warm up the sender and cable connections on one side and then the other to see if I can determinne the side and cause of the error.

I received two sendors on Sunday from Amazon (they are cheap). I now have new spares. Once the side is determined, I intend to fashion a puller to catch the lip of the old one and see if I can pull it off in place. They just press on the hub and need a .005 or .006 clearance on reinstallation which is also one thing I have not checked on the existing ones.

If I am not successful I will follow your recommendations and install a new hub, or maybe two, with new senders.

Thank you for the input. I will let you know what fixes it.
Also waiting for your recommendations. I will need to install in my car
 

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remember reading what a PAIN it was to do rotors on my 08 i think + i had codes for brake sensor on my 2001 jetta $50 + half hr DIY the new one was in so what was GM thinking or not with that design!!!
 

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Discussion Starter · #12 ·
Also waiting for your recommendations. I will need to install in my car
I might be delayed a bit. I have a loaner Tech 2 coming and it should be here Saturday. Also I just found out that I may have to go to Texas this week end which is 1200 miles one way. I have to pick up an older woman who was operated on 2 weeks ago and is too afraid to fly. So it will be a long 4 day drive.

I picked up a small puller this evening that might work, but I may not have time to try it tomorrow. I will definitely post the results when I am finished.
LOL, what GM is always thinking. More money for Dealer Service Departments.
The borrowed Tech 2 arrived by UPS today and It does not work. I can not get ahead on this one. I will call my friend tomorrow and either fix it or go after another one somewhere.
 

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Discussion Starter · #13 ·
Well, I am back. I finally got this borrowed scanner to work but it still has problems. I am mailing it back tomorrow but my friend is sending me another one due here Friday. It will be a TOPCON brand one that also does ABS.

While I had this one working, I was not able to display any active codes, but there were several history codes. What was interesting is the failures were showing the same on both sides. Also there were some failure to communicate codes stored in the history. As this failure has been there for many years and only failed as the temperature got warmer, I have always thought this might be a connection problem instead of a sensor. One anomaly I did spot while running it in the active monitor mode was the voltage. I really was driving watching the speed sensors on a 15 mile trip. The voltage started out in the 10.0 volt range and gradually rose to 13.1 . The scanner also let me concurrently monitor the battery / alternator voltage which was a solid 15.1 and only varied by .1 volt as I turned off and on the headlights and varied the fan speeds. So the alternator is doing it's thing correctly. I was able to finally get one ABS / traction control message on the dash and the scanner could not communicate to the ABS controller.

So now what to do. I first do not now if the voltage displayed was from the ABS controller or the ECU, but I plan to clean up both fender grounds and the inside of the boxes mounted there. Battery cables can not be the problem as the displayed voltage there never changed I now need to understand what cables I be should removing and checking. The ECU or something on the ABS? The ECU never logged any codes.

I am in an area I have never worked on before and I am looking for advice on what to do while I wait for the new scanner to arrive.
Thank You.
 

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So in case this is of any help. I started having ABS errors with my truck, initially they were failed communication error codes from the eBCM. Battery reset would clear it for a month or so. Finally I got the 550 code of death and had to replace the eBCM module.
 

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Discussion Starter · #16 ·
What were the history codes?

When you got the message, on the last trip, did a code also set? If so what was the code?

The ABS Module supplies the 12 volts to the speed sensors.
Well, I almost had to say the dog ate my homework. I wrote the codes doown and brought them in the house. Then could not remember the safe place I put the, It was a very late night. I just found them.
C0035 - Left Front Wheel Speed Circuit Malfunction
C0040 - Right Front Wheel Speed Circuit Malfunction
C0240
C0268
C0899
What were the history codes?

When you got the message, on the last trip, did a code also set? If so what was the code?

The ABS Module supplies the 12 volts to the speed sensors.
C0035 - Left Front Wheel Speed Circuit Malfunction
C0040 - Right Front Wheel Speed Circuit Malfunction
C0240 - Powertrain Control Module Traction Control Not Allowed
C0268 - Pump Motor Circuit Open/Shorted
C0899 - Device Voltage Malfunction
U1000 - Invalid Or Missing Data for Primary Id
U1016 - Lost communication ECM/PCM
U1064 - Lost Communications With Body Control Module

I shipped back the Scan tool today so the above descriptions are from the Internet and not out of the scan tool. I only wrote down the codes before resetting them all. A new scan tool is suppose to arrive here tomorrow.

I have never cleared these before and have not disconnected the battery in several years. So who knows how old these codes are. After having the live data communication failure I had an ABS message and a Traction Control message on the dash and no new codes. I was monitoring live data at the time, primarily the wheel sensors speed and voltage. Those went were not displayable due to the comm failure. The voltage before the failure was 13.0 at the ABS and 15.1 at the alternator / battery.

I have no way of telling if an already set code was set in history again. There were no active codes.
 

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While it is unusual for both front wheel sensors to be defective at the same time, remember that you have had intermittent ABS problems for quite some time without a solution. It is possible that one of the sensors has been bad for a long time and now the other one has become a problem.

If I remember, from my goegraphy classes, Indiana is in snow country and that is where they pave the roads with salt. My guess is that you have two sensors that have been exposed to the elements for 17+ years and will need to be replaced. Keep in mind that half of the sensor installation, the encoder ring, is part of the hub assembly.

C0268, U1000, U1016, U1064 are all related to the Serial Data Bus. Could be a Bus problem or a momentary loss of power. Erase the codes and see what comes back.

C0899 The ABS Module detects voltage below 9.5 volts at the ignition circuit, or the ABS Module detects voltage below 7.3 volts at either front sensor. Again, erase the code and see if it returns.
 

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Discussion Starter · #18 ·
While it is unusual for both front wheel sensors to be defective at the same time, remember that you have had intermittent ABS problems for quite some time without a solution. It is possible that one of the sensors has been bad for a long time and now the other one has become a problem.

If I remember, from my geography classes, Indiana is in snow country and that is where they pave the roads with salt. My guess is that you have two sensors that have been exposed to the elements for 17+ years and will need to be replaced. Keep in mind that half of the sensor installation, the encoder ring, is part of the hub assembly.

C0268, U1000, U1016, U1064 are all related to the Serial Data Bus. Could be a Bus problem or a momentary loss of power. Erase the codes and see what comes back.

C0899 The ABS Module detects voltage below 9.5 volts at the ignition circuit, or the ABS Module detects voltage below 7.3 volts at either front sensor. Again, erase the code and see if it returns.
Salt or as we call it "fender solvent" is a problem in some Indiana counties. In my case our county hardly uses it at all. They get out the salt truck only if the road turns to ice (primarily intersections). So when it snows they plow the roads and we just drive a little slower on what is left. They do sand and cinder some intersections. They do an excellent job. We do not believe in having absolutely dry roads after a snow. I stay off of roads maintained by the state after it snows. The state does spray a liquid pre-salt that dries in place on most of their highways. They only plow when the snow exceeds what the pre-salting does not take care of. I am rural. The closest town is 11 miles and it has one traffic signal. I live 400 feet off of the county road and have to get out my diesel John Deere occasionally to plow my and 4 other neighbor's driveways. I do not bother plowing if the accumulation is less than 8 inches.

So I can say all of my vehicles seldom see salted roads. If they do, they go to the under body car wash ASAP afterwards.

I agree with what you posted. I got out the schematics for the 05 Colorado last night. I could not tell what the static DC voltage, if any, should be. I thought they just generated a small AC voltage (maybe 350 mV or more) from the transducer magnets. If they do put 12 volts on them, they must be looking at the other lead for a difference between the input 12 volts and also at the same time some AC generated by the transducers riding on top the 12 volts DC. It makes sense to put 12 volts on them so the computer can tell when one of them or the circuit is open or shorted to ground.

I got another scanner delivered today. It is a brand new TOPDON 600S. I spent this evening updating all of the software on line. I will probably try tomorrow to figure out how to run it. My friend told me to use and return it to him. If I like it, I can pay him for it. He will just go buy another one.

Thanks everyone for the help. I will keep you advised.
 

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Description from the Manual: The wheel speed sensor receives 12 volts from the electronic brake control module (EBCM) and provides a DC square wave signal back to the module. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed.
 

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Discussion Starter · #20 ·
Thank you for the manual explaination. If it gets down to it, I have a battery powered oscilloscope that I have not used in years. I could see if it still works. I hope not to have to go that far.
 
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