Where does this abs wire go?

[vipmiller803]

Hello all,

 

Having an issue with the buick. I lost abs after having some welding done in the vicinity of a rear abs plug that sits in the body. I am mostly certain the problem isn't the wire running to the sensor itself. Where does the wire run in the body? It isn't under the backseat that I see.

 

Sorry about the bad image quality. My phone blows.

[rich_e777]

I believe it enters the cabin under the rear seat and travels up the body inside a conduit on the passenger side under the carpet. Thats how its setup on my Cutlass.

[vipmiller803]

Where under the rear seat? I have mine removed and don't see it? I don't want to decarpet the whole area just for funzies.

[Heartbeat1991]

It's under the carpet below the rear seat just above the floor pan on my GP.

[vipmiller803]

I didn't realize it was riveted straight to under the seat. Just gotta pull back the carpeting a little more. Oops. Anyway, got that taken care of.

 

Does anyone have an ebcm pinout for the Buick? Chilton is apparently the suck with this.

[Imp558]

I believe these are the parts you're interested in.

Sorry about the crappy phone pictures.

 

 

[vipmiller803]

Yes the first pic was it. Thank you!

 

So it looks like I am hitting a wall with this diagnosis. A little background:

 

I had no abs when I got this car. I knew that the dash lamp had been tampered with (it is always off, including at startup). I found a kinked rear sensor wire, replaced it, and all was well in abs world.

 

Fast forward four years, trailing arm mount separated from rust. The car sat for around a month while I was overseas. I had no reason to believe the abs was not working (it was summer, little to no abs activation). I know it was working for most of summer as I make it a point to listen/feel for the abs initialization. Anyway, had the trailing arm mount welded back together. After the work, I noticed that there was a significant amount of butchery done, including leaving the parking brake bracket dangling and ripping the abs sensor wire straight out, breaking the connector. I figured o well, simple enough to just solder it together. So I did. Now I have measured resistance for all four sensors at the ebcm and the rear ones show ~2k ohms while the fronts show ~1.5k. Given the symmetry, I do not believe there is a sensor problem.

 

Now the only real messy part of the wiring is the part I soldered. Here are my questions:

 

-Do abs sensors have a positive and a negative? I know it is an ac signal. I figured if I somehow switched the connector wires, then I would just be out of phase, which isn't a concern here.

 

-What are some other checks I can make at the ebcm/with a multimeter to test components? I know there are solenoids and motors in the delco VI. I really do not see myself going for a tech 2 any time soon to try and figure this out.

 

-Does tunerpro or anything similar deal with the ebcm? I have tunerpro and can connect to my ecm no problem.

[Imp558]

Bad ABS Module? It seems reasonable that if one inadvertently connected a mig welder to it through a sensor input the ABS Module may not survive.

[vipmiller803]

Bad ABS Module? It seems reasonable that if one inadvertently connected a mig welder to it through a sensor input the ABS Module may not survive.

Thought about that. With those sensor wires being ~28ga, I figured there is no way much amperage made it in there, and I didn't think welders ran very high voltage. I was initially expecting to see some melted wires or connector next to the welds. That would either ground or short the sensor, and the initialization would fail.

 

The good news: As a hail Mary, I decided to just unplug and replug the relay and fuse under the hood. Pleasant surprise, it worked! The relay had a little bit of corrosion on the terminals, but it did seem quiet loose in those terminals. I will bend back those females for a tighter fit (no pun intended) and clean up the relay. I may open up the relay and make sure it is all good. I have had good luck cleaning contacts in those relays.

 

I am always wary of failures that seem like a big coincidence. I don't see how the shop could have done it anyway. Maybe the sensor wires made the ebcm not attempt initialization for long enough that those relay contacts had time to corrode, and by the time I repaired the sensor wiring, the relay had just enough lack of juice to fail at its terminals. Anyway. Let's see if this fix lasts.

 

Thanks for the help! I do prefer having ABS with the snow up here, especially at cruising speeds.