Help: ABS Has me STUMPED, any help will be appreciated!!!

[BigDaddyDiesel]

Ok, here is the story. My ABS light came on and stayed on. Checked the codes and they showed that there was no signal from the left wheel sensor. Common enough issue and can often be fixed with simply cleaning the sensor and putting it back. BUT, since the truck now has 105K on the original sensors I decided to replace them on both sides.

So, today, that is what I did. I replaced both ABS Speed Sensors with new units and went for a drive to see a friend that is the service manager at a Dealer. We hooked the Tech II up cleared the codes, but the ABS light stayed on. SO, with the Tech II hooked up we took it around the parking lot and it through the same code again, "Left side signal" (paraphrased of course).

So, I brought it back home and took everything back off so that I could look down into the sensor hole and spin the hub to check to see if I may have had either some crap in there getting in the way of the signal from the teeth inside the hub. Not only does the grease I put in when I replaced the hub bearing still look outstanding, none of the teeth were worn, chipped or broken in any way. They look excellent!

SOOO, I climbed under the truck and took the connectors loose from the brake control module to see if there was a possibility that maybe either a wire was cut or somehow it may have gotten trash into the connector, ANYTHING that would explain the signal issue. I found absolutely nothing wrong with any of it. At that point I traced the wiring from the controller to the sensor plug where the new sensor plugged into the harness leading to the control module and nothing, no breaks in the wiring, no pinched wiring, no dry rot, nothing.

BUT, it STILL throw the same code. I asked the guys there if they thought the control module had gone bad and they said that if it had gone bad then there would be more than one code. That I would have all kinds of communication failure codes and all that. Also, while hooked up to the Tech II they had it go through an "Automatic Bleed" sequence without issue.

My question is this, WHAT ELSE COULD IT BE???

Within the last year I have installed the following:

NEW Hub Bearings on both sides.
NEW Calipers all the way around.
NEW Drilled and slotted rotors and ceramic pads all the way around.
NEW Speed sensors on both sides of the front.
NEW Master Cylinder.
NEW Fluid when I did the rotors in January.

I am open to ANY advice at this point!!!

Thanks in advance for the help guys!

 

[SSchmi5519]

Whats the code?

 

[DieselD]

Mine did the same thing. I just replaced both front wheel bearings, they came with new sensors, and the problem was fixed!

 

[Cougar281]

To check the wheel speed sensor, disconnect the sensor from the harness and jack the wheel up off the ground.

Check the resistance across the leads going to the sensor. It should read 700-10,000 ohms
Set the DMM to measure A/C voltage. Rotate the wheel by hand. Make sure the reading goes over 100mV.

From there, check the wiring and connector at the EBCM. If the above all checks out, the diagnostic procedure says to replace the EBCM.

 

[BigDaddyDiesel]

C0035 Left side Sensor signal failure or something along those lines.

 

[BigDaddyDiesel]

Thanks guys, yeah, I really don;t want to spend $600 on a new ECMB at this point, but it MAY be necessary.

I guess we will see after I put the multimeter on it.

OF course, I was told that there is a small possibility that the sensor I bought may be bad to start with.

Hope it is something along those lines for REAL....lol

 

[SSchmi5519]

I have a sheet here with a bunch of info about this. I had the same problem, but it didnt throw the light, just a ghost code that was always there.

 

[BigDaddyDiesel]

Yeah, that is what has them stumped too, they can;t get the light to go off at all. They actually leaned toward the fact that these trucks had issue with the cluster and either that OR MAYBE that I have an ignition issue since it is possible that that can cause weird stuff to happen. But, the ignition was changed last year too and the cluster was replaced two years ago. But as we all know, that really means nothing on whether they have issues.

 

[firecapt870]

I had the same problem took mine in and the dealer did a ECM reflash and all is good now:thumb:

 

[Chevy1925]

Yeah, that is what has them stumped too, they can;t get the light to go off at all. They actually leaned toward the fact that these trucks had issue with the cluster and either that OR MAYBE that I have an ignition issue since it is possible that that can cause weird stuff to happen. But, the ignition was changed last year too and the cluster was replaced two years ago. But as we all know, that really means nothing on whether they have issues.

i think your over thinkin it. I have replaced a few hub with band sensor in them. it doesnt take much to kill one of these WSS (wheel speed sensors). literally pulling it out of the wheel bearing housing can kill it or a tap up against anything. i would test the sensor first and described above. if the ohms read in tolerance, carefully remove and swap sensors over to see if the the code stays with the same side. if the RF says its bad now you need a sensor. if it sets teh code for the LF still, check the relutor wheel to make sure its not wobbly (i know you said you checked for debris already, didnt mention this though). Also, im pretty sure you can watch the wheel speed sensor on a the TECHII, id pull those up and watch the RF vs the LF and see what the difference in value is. could say alot depending on what it says

 

[BigDaddyDiesel]

I appreciate all the help guys! I did figure it out though. Like stated, I tested the sensor with a meter and the sensor wasn't working. SO, I went a little deeper assuming that the sensitivity was like you mentioned Chevy1925, and I took it back off and although I had already hit the top of the hub with a wire brush, it wasn't enough; this time I sanded the crap out of it to remove as much corrosion as possible and that did the trick. Once that was done, I pulled out into the road to test it and by the time I hit 15mph the light went out and has not come back on.

It is truly amazing how sensitive those things are! BUT, I am glad to say that it is fixed and the advice here helped me pinpoint where the issue was coming from so that I could get to the solution!

THANKS A MILLION!!! Here's to ya :beer2:

 

[rick67]

Are the hubs you replaced OE or aftermarket?. Same question for the sensors. I have seen cases where OE sensors would not read in aftermarket hubs

 

[rick67]

To check the wheel speed sensor, disconnect the sensor from the harness and jack the wheel up off the ground.

Check the resistance across the leads going to the sensor. It should read 700-10,000 ohms
Set the DMM to measure A/C voltage. Rotate the wheel by hand. Make sure the reading goes over 100mV.

From there, check the wiring and connector at the EBCM. If the above all checks out, the diagnostic procedure says to replace the EBCM.

This is a good test description!

 

[BigDaddyDiesel]

Are the hubs you replaced OE or aftermarket?. Same question for the sensors. I have seen cases where OE sensors would not read in aftermarket hubs

I actually thought about that too, I bought the hubs at Carquest and the sensors were OEM. One of the reasons when I sanded the hub I got into it pretty good thinking maybe the tolerances on the hub may not have been a little off.

And you are right, that description of how to test the sensor was word for word what the dealer told me today as well, AFTER it was posted here and after I had already done it as a result.

 

[rick67]

I appreciate all the help guys! I did figure it out though. Like stated, I tested the sensor with a meter and the sensor wasn't working. SO, I went a little deeper assuming that the sensitivity was like you mentioned Chevy1925, and I took it back off and although I had already hit the top of the hub with a wire brush, it wasn't enough; this time I sanded the crap out of it to remove as much corrosion as possible and that did the trick. Once that was done, I pulled out into the road to test it and by the time I hit 15mph the light went out and has not come back on.

It is truly amazing how sensitive those things are! BUT, I am glad to say that it is fixed and the advice here helped me pinpoint where the issue was coming from so that I could get to the solution!

THANKS A MILLION!!! Here's to ya :beer2:

I have taken a file to them before if the voltage wasn't high enough. Just fixed the cam sensor on a 2002 2.2 S10 cam sensor by cleaning the mounting boss. Saved me $85 by not replacing the sensor.