Dash ABS & brake lights several questions 2001 Blazer LT 4x4 4.3l
 

Ok. So Blaze the wonder car has a problem with the dash ABS & brake lights coming on randomly. I did some research & investigation & found a corroded ground wire attached to the firewall under the air filter. I replaced the end & cleaned the paint & rust from the connection site. The wire itself has some oxidation in the strands no matter how far I cut it back so I want to replace it completely. I followed it into the harness under the underhood fuse box.
Question 1) Can anyone tell me where the EBCM ground wire ultimately originates?

I thought the problem might be cracked solder joints in the Kelsey Hayes EBCM. I carefully removed the cover & inspected & resoldered all of the large solder joints (the really all looked good to begin with.) I see advertising for EBCM repair all over the Internet and instructions to perform the resoldering that I have already done, but I don't see a test procedure for the EBCM.
Question 2) Is there a definitive electrical test that can be performed on the module to determine whether or not it is bad?

I read in one of the posts that leaking vacuum hoses caused these same lights to come on. I have replaced about 12 feet of vacuum hose so far but I haven't thoroughly checked for more leakers.
Question 3) How would a vacuum leak cause these lights to come on?

Blaze & I thank you in advance for your help in answering my questions.

flhTK

If both come on at the same time it's likely the EBCM. I've read from a lot of guys that took at least 2 tries with a magnifying glass to find the cracks in the factory crap solder joints.
I just send mine to one of the $40 places on eBay. Search EBCM repair on there.
They have the equipment to test them.

Think I used gaugerepairman in OK. I'm in WI and have no affiliation with them. Just know what worked for me. You can drive the vehicle for the 4-5 day it takes with shipping.

Actually:
Brian's speedometer
1004 S. CADDO ST.
Muldrow,OK.74948
918-427-9889

lifetime warranty on abs module as long as you own it
ONE DAY or the SAME DAY turn around

Welcome to the forum. The light comes on when an abs code is triggered. They are automatically cleared when the truck is shut off. Drive until the light comes on and have it scanned with an abs capable scanner before shutting the truck off. If you shut it off, then connect the scanner and turn the key to run there won't be any codes present. Getting the codes is the best answer I have for question #2.

Thanks Rusty
 

Rusty, your response clears up the confusion. I'll keep the scan tool in the car & check the next time the lights come on. When I first got her she showed the CO265 code. I couldn't understand until now why the code never reappeared.

Tom

ABS & Brake light don't set code.
 

So today I took Blaze for a ride & trompped on the brakes in the snow activating the ABS momentarily before setting the ABS & Brake lights. I drove her home with the lights on & while still running attached my scan tool, but alas NO CODE set!
I need a definitive way to test the module before I replace it.

I'd check the brake switch by the pedal next.

Go to BBB Industries and download the wiring diagram for your brakes. My schematics are for a 98 and there are differences so mine won't work for you. However, the ground wire you were cleaning is G110 and is the power ground for the EBCM. The signal ground G105 is on rear of passenger side head on my '98. I believe it is the same for yours. PITA to get to. C0265 is EBCM Relay Circuit. I would do a ground to ground voltage drop test with a voltmeter to see if the corrosion in that wire is the problem. See my note below. Backprobe the ground wire at the connector with the connector plugged in using a T-pin or some other needle like probe. Note that this is the main power ground for the EBCM. Place the other lead for your volt meter on the B(-) post. Key on, engine off (KOEO), apply the brake. The volt meter should display 0 volts (+/- 100mv). If you get any voltage, there is a problem with that ground wire. I would do the same for the signal ground wire.

Fundamentally your volt meter is reading the potential between the two leads. If there is any voltage (potential) displayed that means the EBCM ground wire (either power ground or signal ground) is not allowing the current to travel through the wire, to its grounding location, and then back to the battery. The voltage is "dropping" and the meter is reading that drop.

NOTE: If you do not pay close attention to what you are doing, you could fry a component. I highly recommend you get the complete wiring diagram for that circuit and study it to ensure you are probing correctly, etc. Alldatadiy.com is one place you can subscribe to get your whole technical manual. I think it's less than $20 a year. I don't have enough experience with BBB industries to bet the farm on them or not. If you are not experienced in the use of a volt meter, you might want to watch some You Tube videos on voltage drop testing before you proceed. Most of the videos I think are focused on voltage drop on the power side. You want to do ground to ground though since your ground wire is suspect.

I'm pretty convinced it's the EBCM as well. The brake switch is the last cheap thing I could think of. The abs systems are the same for 2000 and 2001.

Clarification question rockp2
 

Just to clarify, you are saying to perform the voltage drop test on the wire you identify as G110 correct?


Clarification question

Just to clarify, the voltage drop test described doesn't check the EBCM itself (I should've pointed that out). Rather it checks to see if there is high resistance in the ground wire itself between the EBCM and the ground G110. If there is a voltage drop, then there is probably corrosion in the wire and replacing the ground wire could solve the problem. The EBCM is susceptible to high resistance.

Theoretically, if he did have a voltage reading above 100mv (indicating high resistance in the ground wire) he could:

1. Leave the voltmeter installed as described
2. Take a fused jumper wire and attached to the B(-) post
3. Starting at the G110 side of the ground wire, cut/strip the ground wire back a couple inches at a time
4. Connect the fused jumper from B(-) to the ground wire at the cut/strip
5. KOEO, foot on brake, check the volt meter (obviously this will be much easier with a helper)

Once the volt meter drops to 0 volts (+/- 100mv), that's the spot he cop splice in a new wire and run the new wire to G110. Then do the original voltage drop again to confirm he has achieved good ground. Then disconnect the volt meter (not forgetting to remove the T-pin!), and see if he has a fix.