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Discussion Starter · #1 ·
Quick history: I've got some other posts about this truck. (2003 2500HD 4x4 ext cab short bed) I recently bought it at an auction, it was a seized by some drug task force and they auctioned it off. So...I get to enjoy being a detective to run down problems.

I bought it knowing ABS light and brake light were sometimes on. I get it home and start really digging and both front sensor wires are disconnected. So..I sprayed them with some cleaner and plugged them in. They were not that dirty anyway...but figured it was good measure.

Lights went out. I cleared all codes with my tablet and considered myself a genius!!!

But wait..there's more...

Couple weeks go by and the ABS light pops on. I run the code and it's the right front. I dig more and can see there is still wheel speed and the wheel speed matches. So...not sure why I'm getting a code.

Code will clear and sometimes stay gone for day or two.

Fast forward to now my oldest daughter is primarily driving the truck. She said ABS light comes on and goes off from time to time. Now she says sometimes the parking brake light comes on..when it's not.

She says brakes still work fine.

I have checked for play and noise in the hubs in front and they seem solid. If they were iffy..I'd just change them to get new hubs and sensors. Part of me says just to do this so I know I'm good there, since my daughter wants to keep this truck for a while.

If the tablet said it couldn't "see" the sensor or get a reading I'd change it in a heartbeat as well..but that doesn't seem to be the case.

Tonight I plan to look at the connections again..and check everything over visually again.

My question is...is there other troubleshooting I should do prior to swapping out hubs or just the sensor. I've done hubs before on other 2500 HDs (I also have an LLY) I've never done "just the sensor".

But wait...there is more. Very high chance that a buffoon has worked on these brakes before. I knew there was an issue with back brakes as well (disclosed at auction) and there was a bad grinding on the way home from auction.

I still can't believe it...but some pads were in backwards on one side. Yes...metal up against the rotor with pad facing out towards outside of the truck.. (so I've already done new calipers, hoses, pads and rotors on the back)

I mean...I've screwed up mechanic work before but...brake pad in backwards???

Hope you guys can help...appreciate all of you!!!

Best,

NH
 

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Discussion Starter · #2 ·
I wish I had taken more pics when it was in the truck. Back caliper was really loose as well (on the side with backwards pad).


No idea how this is related to a front ABS light (primarily right side)....I don't believe the left has some on since I plugged everything in.

Posting it mainly for "hey..look what I found on this truck" and also to say that we should ASSUME NOTHING about the front...since I've found some crazy in other places

Best,

NH
 

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The ABS code number would help us help you, but...
There are, in my mind, two ways to set a sensor fault
1) broken circuit...ABS and BRAKE light on at startup
2) poor signal...ABS and BRAKE light on once over, say, between 6 and 20mph.

The ABS lamp coming on for an ABS fault "should" also illuminate the BRAKE lamp.
The BRAKE lamp coming on for low fluid level or P brake engaged "should not" illuminate the ABS light.

An unplugged sensor "should" always keep both the ABS and BRAKE light illuminated after startup.

As for "seeing" the road speed from each sensor, the "clue" usually rears up as you decelerate from 10mph to 3mph. Sensor out of range due to mount rust or a sloppy wheel bearing begins as a low speed signal loss.

So....back to the fault code. It will narrow down not only which sensor, but also confirm if the circuit is complete or not.

At startup, the EBCM (Electronic Brake Control Module) self tests for circuit, valve and internal integrity.
 
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Discussion Starter · #4 ·
C0040 seems to be the recurring code.

I'm trying to get my original code scan with all the historical stuff. Getting the report of my tablet is proving difficult.

Thanks for information. Hope the actual code narrows it down.

Best,

NH
 

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C0040 say circuit to right front wheel open.
Broken wire in the insulation, corrosion at the wire crimp in the connector(s), internally open sensor, damaged wiring from shock tower to the EBCM, damaged sensor to shock tower harness, corrosion in the EBCM connector, etc.
Since it comes and goes, the harness from sensor to the shock tower is my first guess at a suspect.
 

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Discussion Starter · #6 ·
So it would seem possible that it is a bad sensor, but unlikely because of the coming and going?

I've been driving it when it came on and I've not been able to establish a pattern. Not because of a bump or wet or anything like that.

So sounds like a really good visual inspection all up the wire harness and then go from there. Does that sound about right?

NH
 

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Continuity test of sensor harness while flexing the wire.
 
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