2000 4.8 Yukon ABS Module

[wayaboveme]

Greetings!

I've read many of the posts on the forum re: the ABS Module going bad resulting in the Brake Light and ABS Light remaining lit on the dash. Couple of questions:

1. Any preferences between using Module Master vs. ABS Fixer to get my module re-built?

2. MM told me to get the OEM from GM for confirmation. ABS Fixer told me to take it to a mechanic to see codes (1. Pump Running Failure or 2. CO265). I'm little leary that MM didn't tell me to do that and just assumed that the ABS was broken and I should just remove it and send it in. Who's right?

3. Also a little leary on trying to remove this myself. My unit is under driver door on top of the brake lines. Is it a difficult job (I can handle most things with good pictures and instructions) or should I take it in to local mechanic and have him remove it to send in?

Thanks and would appreciate any other advice.

Will

[wayaboveme]

Just got off phone with GMC Service Advisor. He says he doubts problem is my ABS Module stating that once that goes bad, my lights would stay on all the time. In my case, the lights come on intermittently and then stay on until I turn the engine off. When I re-start, the lights might not come on at all, within 3 minutes or after 15 minutes of driving. Those dang lights actually started showing 1 year ago but problem went away for 9 months before resurfacing the last 2 weeks.

He also said he thinks it is only a 25% chance problem is ABS and much bigger chance that it is a speed sensor problem in one of my wheels but wouldn't know until pulling the codes and doing an inspection.

Thoughts? What are wheel speed sensors?

[DVSNCYNIKL]

Originally Posted by wayaboveme

Just got off phone with GMC Service Advisor. He says he doubts problem is my ABS Module stating that once that goes bad, my lights would stay on all the time. In my case, the lights come on intermittently and then stay on until I turn the engine off. When I re-start, the lights might not come on at all, within 3 minutes or after 15 minutes of driving. Those dang lights actually started showing 1 year ago but problem went away for 9 months before resurfacing the last 2 weeks.

He also said he thinks it is only a 25% chance problem is ABS and much bigger chance that it is a speed sensor problem in one of my wheels but wouldn't know until pulling the codes and doing an inspection.

Thoughts? What are wheel speed sensors?

If you're trying to avoid spending money, you can check for yourself, but there is a little work involved and you will need some time.

Start by jacking up one tire and remove the tire. Behind your brake disc or rotor, toward the bottom, you should see a wire that runs to a sensor. This sensor, if it gets dirty or the grooves that it reads has debris, can trigger the light in your dash. Start by checking the groves or little boxes for debris, if any, remove. The wire that is attached to the sensor, remove and clean off. Also check sensor for dirt and remove. Now for the time consuming part, you have to do this for each tire. While it may be time consuming, this could lead to the end of your issues. Let me know if this works.

[blazee]

It sounds like something is failing when the system does it's self test. You can check the front wheel speed sensors with a voltmeter. Jack the front until the tire clears the ground, set your meter to read millivolts and connect the leads to the wires coming from the speed sensor. Spin the wheel by hand at a rate of about one revolution per second, the meter should read at least 350 mv. If less, remove the sensor and clean out any debris, and retest. Repeat for the other side.

[wayaboveme]

Thanks for the response. I'm looking online for pictures of the Sensor and there seems to be loads of them. Do you have a link for what I should be looking for? Thanks!

Originally Posted by DVSNCYNIKL

If you're trying to avoid spending money, you can check for yourself, but there is a little work involved and you will need some time.

Start by jacking up one tire and remove the tire. Behind your brake disc or rotor, toward the bottom, you should see a wire that runs to a sensor. This sensor, if it gets dirty or the grooves that it reads has debris, can trigger the light in your dash. Start by checking the groves or little boxes for debris, if any, remove. The wire that is attached to the sensor, remove and clean off. Also check sensor for dirt and remove. Now for the time consuming part, you have to do this for each tire. While it may be time consuming, this could lead to the end of your issues. Let me know if this works.

[blazee]

You can see where it enters the hub in this picture.

[wayaboveme]

Even more interesting news. Stopped at local mechanic on way home last night. He ran the codes. Came up as C0265. Sent this to "Don" at [email protected]. Came upon Don on Ebay when I was looking for others that refurbish the ABS Module. Below is his comment:

Hi Will,
Your problem is most likely a bad ground at the Connection from the Pump to the frame. I have attached C0265 fault code for you to review. We have found when this ground is corrected, all worked well after a few key cycles and 15 to 20 minutes of driving. Hope this helps
Don

Here are the links to what Don's attachment said:

http://i309.photobucket.com/albums/k...265_Page_2.jpg
http://i309.photobucket.com/albums/k...265_Page_1.jpg
http://i309.photobucket.com/albums/k...265_Page_3.jpg

Very interesting if you ask me. If it is true, a whole bunch of very expensive ABS units may have been replaced unnecessarily. We'll see I suppose. Thanks for the help and I'll be reporting back as I discover items this weekend under the truck. Thanks!!!

[blazee]

Wow, old age is catching up to me. I completely forgot about GM having those problems. The ground issue is a pretty wide spread problem and has caused a lot of necessary repairs.

http://www.automotiveforums.com/vbul...21&postcount=2

[wayaboveme]

Well, fingers crossed, did the work yesterday and so far so good. Took a bit to locate what I think was the ground wire. First wire I found bolted to the frame ended up being for the fuel pump. Had the engine started to see if the ABS light iluminated when I removed the ground, it didn't, but the engine started sputtering! Cleaned the ground anyway and put it back on. Engine now good again. Whew!

I pulled off the next wire choice (and only other one I could find near the ABS Module) and ABS light illuminated (even though the brake light did not... curious). Cleaned it up really good and re-attached.

I'll report back in a week or two to confirm but looking good so far!

GO ORIOLES!

[wayaboveme]

Back at ground zero I guess. Light coming on more frequently now. Will check speed sensors first before replacing module. Interestingly enough, when the light on, ABS definitely does NOT work. Tried the brakes w/ light off and with light on and difference w/ and w/o ABS is very discernable. WD

Originally Posted by wayaboveme

Well, fingers crossed, did the work yesterday and so far so good. Took a bit to locate what I think was the ground wire. First wire I found bolted to the frame ended up being for the fuel pump. Had the engine started to see if the ABS light iluminated when I removed the ground, it didn't, but the engine started sputtering! Cleaned the ground anyway and put it back on. Engine now good again. Whew!

I pulled off the next wire choice (and only other one I could find near the ABS Module) and ABS light illuminated (even though the brake light did not... curious). Cleaned it up really good and re-attached.

I'll report back in a week or two to confirm but looking good so far!

GO ORIOLES!

[procaddytech]

Sorry to say but it sounds like you are gonna need at least an EBCM or possibly both an EBCM and BPMV. Espicially if you have a good ground at G110 and a solid power supply to module. May need module calibrated to you tire sizes.

[wayaboveme]

Just to be clear, is an EBCM (Electronic Brake Control Module?) the same as the ABS Module? And, what is the BPMV?

Originally Posted by procaddytech

Sorry to say but it sounds like you are gonna need at least an EBCM or possibly both an EBCM and BPMV. Espicially if you have a good ground at G110 and a solid power supply to module. May need module calibrated to you tire sizes.

[procaddytech]

Sorry! Yes, EBCM is Electronic Brake Control Module for ABS. BPMV is Brake Pressure Modulator Vave that the module bolts to. BPMV contains all the valves and the pump motor and the brake lines bolt to it. EBCM cotains the motor relay and the system software and bolts to top of BPMV. If the motor resistance is good (0.3-1.0 ohm, measured with pigtail disconnected, through motor) and not shorted to the case then you probably just need the EBCM.

[wayaboveme]

Thank you pro-caddy. Your help is very much appreciated. Do you subscribe to the earlier advice I was given to take each tire off and inspect/clean the speed sensors before replacing the ABS module?

Originally Posted by procaddytech

Sorry! Yes, EBCM is Electronic Brake Control Module for ABS. BPMV is Brake Pressure Modulator Vave that the module bolts to. BPMV contains all the valves and the pump motor and the brake lines bolt to it. EBCM cotains the motor relay and the system software and bolts to top of BPMV. If the motor resistance is good (0.3-1.0 ohm, measured with pigtail disconnected, through motor) and not shorted to the case then you probably just need the EBCM.

[procaddytech]

Do you subscribe to the earlier advice I was given to take each tire off and inspect/clean the speed sensors before replacing the ABS module?

Not for a repeat C0265 ony. You would have other codes or unwanted ABS activation with no codes if a wheel speed sensor was faulty or dropping out. These trucks do have problems with corrosion building up under the front wheel speed sensors causing specific wheel speed sensor codes and/or unwanted activation when slowing to a stop, but you have neither of these symptoms.