If the sway bar end links are good, the clunk is often the sway bar bushings, a common problem, can be tricky to get the correct size replacements. I had these replaced on an 08 at pretty low miles.

GM calls the sway bar a stabilizer bar I think. My Chevy mechanic friend calls the end links “rattle links.”

Got curious about C0899, I was noodling around the interweb and found more than one claim that the SERVICE ESC & TRACTION CONTROL & ABS warning lights were caused by the C0899 EBCM problem and not the other way around, so maybe try to fix C0899 first? Lots of reports of wiring and connectors causing it.

 

Stabilizer bar is what I was told is the correct name... couldn't remember. Thanks for the refresher. But I'll probably keep calling it a sway bar.

 

Freshened the ground from the block to the frame just forward of the EBCM. Got very low OHM readings between them and the ground lug down and to the right of the under hood load center.

Then Put the new "BlueDriver" on the car. Couldn't get the app to sync to it using my ChromeBook. But it worked fine with my android phone.

It scanned everything... and I mean everything:

Got the same two codes from the EBCM:

C0899 (history code... wasn't current)
C0335 (drivers front speed sensor... active)

Then the BCM (body control Module) had history codes... none current:

B1325
B1517



I cleared all the codes... only
C0335 came back.

-----------------------------

I pulled the ABS harness from the EBCM and did the procedures on Pages 9-11 and 15-17 on the detailed PDF DonBrew posted above... (checking voltages and impedances).

The voltage between hot and the low terminal of the speed sensor came back above 1V
And I Had infinate resistance between the two speed sensor terminals...

Both of those point to a bad speed sensor...

So I ordered a Moog Wheel Hub/bearing assy.

--------

When I connected the harness back to the EBCM (and by the way its nearly impossible to get to that thing to work on it... especially when its old and doesn't want to come apart)...
pulled codes... had a ton of communication codes between every module and the EBCM (as expected).

Cleared them all, and only C0335 came back. (as expected).


I think the C0889 code (and B1325 B1517) were history hold overs from trouble shooting the weak battery and were fixed once I put the new battery in a few weeks ago.

Hope this helps someone.

 

Guessing those last 2 codes (above in red) are typos since they don't match up to the C0335 or C0899.

 

Yes... edited the other post to correct those typos.

Good catch...

 

Oh and I forgot to mention, last time I started the car I probed the hot terminal at the load center to the three ground points (front of engine... forward frame by EBCM... and wheel well to the right of the load center) and got well over 14.2VDC at all of them... the alternator is atleast putting out the requisite voltage at idle...

I'm convinced all the the low voltage codes were hold overs from the earlier battery issues.

Glad to have a good code reader now so that I can monitor these things and know what the car is trying to tell me is wrong.

 

So, are you saying the C0899 was a history code all along? History codes clear themselves after 100 or so cold starts, and do nothing beyond advising that it happened in the past.

 

Yes... by the time I got a good coder reader and could scan the ABS system my self it was a history code...

The guy at the auto parts place who scanned it, just told me the codes and ran along to something else.... I waited to get my own code reader and that is when I learned it was a history code... which I'd guess ties back to the battery replacement I explained in my original post.

Also when probing the ABS connector all the hot pins were showing 12.6+ VDC when the ignition was on... The wiring and grounds are good (and I freshened the grounds at the beginning of trouble shooting). So perhaps its possible I cleared up a bad ground... but I really suspect it was just a persisting history code from when I trouble shot the bad battery.

Thanks for your persistent assistance.

 

Much ado about nothing.

 

another random question... I read somewhere that there is a ground under the driver's seat for some stuff... but it seems to be covered by carpet... how would one get at it inorder to freshen it

(I had a 94 grand am that would do random weird stuff... once the ground under the drivers seat was found and freshened it all went away) So I'm just curious about this one...