Disney

2001 Yukon ABS no comm

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@Ashley P I'm working on my mutt of a 2001 Yukon. I have an ABD light on. I plug up and I get no communication on the ABS. I cleaned and reset the ground wire that is the common cause. I disconnected the two pin connector from the ABS module on the frame and ohm'd that out and I have near 0 between the connector and the terminal on the ground. I checked and have 12v+ at that connector too. That leaves me lost. Where should I look for no comm next?

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Good grief Charlie Brown, have we suffered an EMP attack?  I've got 3 vehicles with similar issues...

Any codes?  I presume the ECM and/or BCM give a U code for no ABS comm?  That code will get you a flow chart (maybe).

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Image above is broken link. 

 

I got no ABS codes from any systems. ECM and BCM both show no codes. Transfer cas controller shows two codes, but it's got no Xfer case so that's to be expected.

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Figured my link was bad.  Back to drawing board...

When I get a no comm, I look for all power supplies and all grounds to the module.  Usually, one is missing.  If they're good, the comm wires themselves should be ohmed to the "hub" (main comm module, or OBD II connector sometimes).  If no problem there, the module is dead.

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TBH, I stared at these diagrams for a while and never really made out which wires I should have power and ground at. It looks like that A1 C2 wire is the only 12v+ and I didn't see a 12V- other than the big one, A-C1. Is that your read on it too?

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My read also.

The diagrams list traction control as optional.  That module is tied into the ABS.  Often a module can die and I suppose short the signal to ground, effectively downing a section of comm.  It's much like the electric grid in a rural area.  Some houses may be dark but there's probably only one tree on the lines. 

You can ohm the comm wire from B6-C2  to term E at the DLC.   Light blue all the way.

Those modules are likely cheaper than dirt.  The early models (2000 ish) used to fail with the pump motor running continuously.  I haven't seen one no comm yet.

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Power passes through C102.   That's located under the junction block (under hood).   It's rectangular w/8 term.

50% chance of a mouse nest there...

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That second picture is the only 8 pin I see in there. It was NOT connected when I lifted the fuse block. I connected it and like He-Man I now have THE POWER! But, I still have the ABS light on. I dont have the scanner here so I cant pull codes or see if its online now. I do hear and feel a click in the abs unit when I plug the connector in so that's good.

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Posted (edited)

Well, seems like you're on the way to fixed.  Wanna try a battery disconnect to clear codes?  I pull one cable and touch it to the other to wipe capacitors. 

 

My world of EMP stuff continues with the G6 Ecotech that I found had BOTH cam sensors bad (and the starter went out shortly into diagnosis). At least it's fixed.  Now to get back to the Duramax with no injector pulse and check out mom's house that did get hit by lightning.  It came down the metal roof and jumped both to the poplar tree and to the porch, blowing the wooden hand rail apart.  I'm thankful it didn't burn down.

Edited by Ashley P

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Wanna know how rediculous my problems are?   A week ago I diagnosed a truck...it had no brake fluid left and rotten brake lines.  I just got the lines on, system vacuum bled, and it's still got ABS and RBWL on.  I hook up scanner.........NO COMM!   What truck?  2001 Tahoe.  :doh:

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Posted (edited)

OH COME ON!!!! (Clean and maybe replace the ground on the frame under the drivers door?)

 

Hey, got any insight on a B0036? ADS open/shorted. I can't find the ADS.. Supposed to be left front???

Edited by Disney

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Posted (edited)

30 minutes ago, Disney said:

OH COME ON!!!! (Clean and maybe replace the ground on the frame under the drivers door?)

 

Hey, got any insight on a B0036? ADS open/shorted. I can't find the ADS.. Supposed to be left front???

Under the core support, I think.  Diagnostic chart just says "front".  Those go bad once in a while...weakest link I think.

Service 4WD, often either the switch (I keep one for test) or encoder motor sensor (sensor available separately).  What codes?

Edited by Ashley P
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