ABS and Brake lights intermittently turning on and off

2001 CHEVROLET ASTRO
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3FORFRED
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I have a 2001 Astro with approximately 148,000 mi, and both the ABS and brake lights on the dash have been going on and off intermittently for several weeks now. I have checked the fluid and it is full. It's dark and needs to be flushed, but, it is full. I have also removed both front wheels and have cleaned the sensors with brake cleaner and contact cleaner as well as removing them and scraping the mounting plate to ensure a good contact. This van is rear wheel drive and has disc in the front and drums in the back. I don't see any sensors on the back so I assume that sensors only go on the disc brakes. I have unplugged all of the connectors at the ABS module and cleaned them with contact cleaner as well. Whenever I disconnect the battery for any of this work, the lights stay off for as long as several days and then they come back on. I have had a mechanic scan it and he says that the EBCM is going bad. He didn't write down or remember the codes so I can't look them up. Is there anything that I have missed? I can't find where the sensors plug in to check those connections. I have gotten so many different opinions and answers that I'm not sure where to turn next.

Thanks for your help,

Fred
Oct 18, 2007 at 4:49 AM
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CHEVY22
  • ✓Experienced Mechanic
  • 1,375 POSTS
the EBCM is electronic brake control module and is on top of the ABS module there really is nothing to clean if it's bad its bad and needs to be replaced. also, the rear should have ABS but it's in the differential and works off a reluctor ring for speed signal. look at the diff for a connector check around for prices on the EBCM before you buy one , and check that against a GM re-manufactured online at gmpartsdirect.com


Jim
Oct 18, 2007 at 9:25 AM
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3FORFRED
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Thanks for your ideas. I can't seem to locate the sensor that is at the differential. I'm going to go back under the car again and see if I can find it. I am also having a hard time locating the connectors for these sensors so I can put my DVM on them to measure the output voltage. Any assistance on where they are located is appreciated.

Thanks again,

Fred
Oct 30, 2007 at 3:15 PM
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3FORFRED
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I have found a service that I can ship it to in Massachusetts and they'll rebuild it for $99.00 plus shipping. Seems there is a switch that goes bad inside the EBCM. I have gotten the code C0265 which refers to an internal relay in the unit itself. I'm at the end of my rope so I'm going to give this one a try. I like this idea because if it does work, it already matches my computer and I don't have to have it reprogrammed. If I buy a new one, I have to pay someone an hour labor to reprogram it. I'll post if it works. If not, I'm out about $130.00 and still at square one.
Nov 11, 2007 at 3:03 PM
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3FORFRED
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Sorry I haven't posted in a while. I haven't sent the part out (holidays, college tuition and all that good stuff). I'll be sending after the first of the year and I'll post the results then.

Have a good holiday!
Dec 19, 2007 at 2:43 PM
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FRED DALLYN
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Fred. I have a 2001 AWD with 150,000 kms and the same problem. Lights come on after driving for 10 minutes or so. Sometimes after a bump and sometimes not. Scan shows that a relay is at fault. Tried to contact the guy who does exchange modules but no reply. Just came back from the dealer with the cost of the part at trade $800.00. list $1,100.00. Yikes. Dealer says they sell very few,but there is one in the warehouse. This is in Vancouver BC.
Does this thing affect the AWD function?

Another Fred.
Apr 4, 2008 at 6:10 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
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Hi,

The ABS module affects the AWD function when you have stability control. In this case, I see no correlation with the AWD unit. Also, is the code which was retrieved a C0265? As you are already aware, the relates to the ABS relay. Honestly, it isn't common for them to go bad. However, it isn't odd for there to be wiring issues. Thoroughly inspect connections and circuitry that may cause an malfunction. The reason I suggest this is because you indicated it can sometimes happen when you hit bumps.

Here is a link that explains how to test and check wiring:


https://www.2carpros.com/articles/how-to-check-wiring

If you look at pic 1, it shows EBCM. Make sure the connections are tight, not corroded, and there is no damage to the pins within the plug.

I hope this helps. Let me know if you have other questions.

Take care,
Joe
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Mar 26, 2020 at 12:47 PM
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