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Discussion Starter #1
My 2013 LTZ just started having an issue where when I start out from a stop, it feels like the transmission is slipping or grinding unless I ease into it really slowly. And it seems to happen nearly every time if the wheels are turned to the left, but doesn't seem to do it much (or at all) when the wheels are straight or turned right.

Initially I thought it was a transmission issue and I took it to a mechanic who also agreed it was the transmission starting to go bad and gave me a quote to replace it, but I wasn't ready to do that, and in the few days since then, I'm starting to wonder if it's something else.

I saw another thread in the Drivetrain forum:
https://www.impalaforums.com/8th-gen-drivetrain/1846269-slippage-on-take-off-when-turning.html @jtrosky
That sounds similar to my issue and I'm wondering if something as simple as replacing some wiring would fix this problem rather than having to spend $4k on a replacement tranny.

Also, yesterday the Service ABS and Service Traction Control and Service Stabilitrak lights all came on a the same time. Does that shed any light on the possible diagnosis?

Any thoughts?
 

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Also, yesterday the Service ABS and Service Traction Control and Service Stabilitrak lights all came on a the same time. Does that shed any light on the possible diagnosis?

Any thoughts?
To me, these new symptoms all but confirm it's one of the front ABS speed sensor harnesses.

The grinding noise is the traction control firing, which applies the brakes, and that is probably what makes it feel like the transmission is slipping.

The bad sensor connection makes the computer think there's a wheel spinning so it applies the brakes, which also makes the grinding sound.

Having the steering wheel turned stretches the harness which exacerbates the bad connection, so that's why you feel it more going left.

You still need to confirm which harness it is, but that's not too difficult. On both front hubs, you'll need to pull the wires out of the loom and inspect the last few feet of each one looking for a broken spot, or a flimsy spot where the wire is broken inside the still-intact insulation.

HTH.

Doug

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Agree with Doug - it sure does sound like it might just be a simple speed-sensor wiring harness issue. Usually, but not always, if it happens when turning left, it's the passenger side harness and if it happens when turning right, it's the drivers side. Again, not always though, so if you can check for codes - they might tell you exactly which one is the problem without even testing them.

I'm curious - how many miles are on your car?
 

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Discussion Starter #4
Agree with Doug - it sure does sound like it might just be a simple speed-sensor wiring harness issue. Usually, but not always, if it happens when turning left, it's the passenger side harness and if it happens when turning right, it's the drivers side. Again, not always though, so if you can check for codes - they might tell you exactly which one is the problem without even testing them.

I'm curious - how many miles are on your car?
107,000 miles

I sure hope it's something relatively simple like this and not my tranny going bad. I'm comfortable working with home wiring, but I haven't done much wiring in cars. Seems like the connections/soldering would need to be a lot more durable than simply twisting on a wire nut like you can do with residential electrical connections.

Is the part I would need to buy called the speed sensor wiring harness?
 

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107,000 miles



I sure hope it's something relatively simple like this and not my tranny going bad. I'm comfortable working with home wiring, but I haven't done much wiring in cars. Seems like the connections/soldering would need to be a lot more durable than simply twisting on a wire nut like you can do with residential electrical connections.



Is the part I would need to buy called the speed sensor wiring harness?
Yes, that is what it's called. Here is an example from Ebay - this particular one even comes with some heat-shrink to seal up the connection after you've repaired it. You would need to solder the wires after you splice in the replacement pigtail.

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/222901365294

Normally, I try to use OEM parts, but to be honest, the OEM harnesses don't last so long anyway, so I used a very cheap no-name brand part when I replaced my drivers side harness and haven't had any further issues (I paid like $14 for two of them at the time). I'm sure you get them on Amazon too if you use Amazon. Very common replacement part.

There is a link in the post you quoted that shows a few pictures from when I replaced mine.

Hope that helps. Don't hesitate to ask questions if you have any!
 

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Discussion Starter #6
After some more driving and experimenting, it definitely only does it when turning right and only at very slow speeds, like maneuvering out of a parking spot or something. Above 5 mph it doesn't make the sound anymore. But I'm not sure it's the traction control or ABS as previously discussed. It sounds like something scraping. And shouldn't I feel the pulsing if it's applying ABS?
 

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Discussion Starter #7
Another question: Assuming it is the wiring harness previously discussed, is there risk of more damage if I don't replace it right away? If I only hear that scraping sound those few times I'm starting from a stop and turning left (actual left turns while driving are usually fine because I can get some speed before turning), then is it damaging anything when I hear that?
 

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After some more driving and experimenting, it definitely only does it when turning right and only at very slow speeds, like maneuvering out of a parking spot or something. Above 5 mph it doesn't make the sound anymore. But I'm not sure it's the traction control or ABS as previously discussed. It sounds like something scraping. And shouldn't I feel the pulsing if it's applying ABS?
The scraping sound is the traction control function applying the brakes. With the wheels cut hard, as typically happens when you're getting into/out of a parking spot, the bad wire gets stretched which disturbs the signal causing the computer to think the wheel is spinning resulting in the traction control function applying the brakes.

That makes a different noise than the ABS (which pulses the brakes to release one that is locked or nearly locked). The traction control sound is very much as you describe, a grinding or scraping sound. The ABS makes more of low pitched whirring sound. (A Google search for the sound was fruitless :) )

If you feel anything else when the grinding occurs, you may notice the steering wheel pulling to one side, whichever side is being braked.

HTH.

Doug

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Based on your latest descriptions, I can almost guarantee it's the ABS speed sensor wiring - and most likely the driver side. While it won't really hurt anything to leave it be (other than to wear out your ABS system!), it will get worse - with mine, it got to the point where the car sometimes wouldn't want to go, even at higher speeds. For the $15 and 30 minutes it takes to fix it, I'd recommend getting it fixed - it can became a safety issue.
 

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Based on your latest descriptions, I can almost guarantee it's the ABS speed sensor wiring - and most likely the driver side. While it won't really hurt anything to leave it be (other than to wear out your ABS system!), it will get worse - with mine, it got to the point where the car sometimes wouldn't want to go, even at higher speeds. For the $15 and 30 minutes it takes to fix it, I'd recommend getting it fixed - it can became a safety issue.
Just to be absolutely clear for the OP, DevdogAZ, the ABS speed sensors provide input to both the ABS and traction control functions.

I agree, getting the cable(s) repaired promptly should be a priority.

It's one thing to not have ABS - I've owned many vehicles without it - but having the traction control apply the brakes at the wrong time could be dangerous.

Doug

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Discussion Starter #13
Finally found some time to pull my front wheels and take a look at the cables. I'm not seeing anywhere along the cable (on either side) where it looks especially worn or fragile. With the wheels off, is there any way for me to do a test to see if I can definitively diagnose the issue?

Driver's Side:


Passenger Side:



Also, if/when I do replace those wiring harnesses, where is the best place to cut and splice? Should that be done closer to the wheel and plug connection, or farther up on the end that connects to the car?

Driver's Side:


Passenger's Side:
 

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You definitely won't see anything wrong with the wires just by looking at them. Hell, I even completely took mine apart after replacing it and I couldn't see anything wrong with it, even though replacing it defintiely solved the issue. The problem is that the actual wire underneath the wire protection and wire insulation actually breaks - or maybe not even break all of the way, but damaged somehow (like I said, I couldn't even find the issue when I tore the old one apart).

One thing that I was able to do to "confirm" the issue is to use a multimeter on the wire and while bending the wire in one spot, the multimeter reading would go crazy.

I would replace the wire about 12 inches or more from the connector at the wheel. Usually, the wire is messed up near the plactic zip tie things that hold the wire down. Over time, from the wheel turning back and forth, those areas get stressed and caused the wire to break inside the insulation.

Honestly, it's probably quicker to just replace it than it is to try and find the issue. :)

One other thing that you could do is check the computer for codes (autozone will do it for you for free if you don't have a code reader). It might even tell you for sure which wheel it is. There can be codes stored even though there is no check engine light...
 

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After some more driving and experimenting, it definitely only does it when turning right and only at very slow speeds, like maneuvering out of a parking spot or something. Above 5 mph it doesn't make the sound anymore.
I'd bet it is a speed sensor wire. Mine did the exact same thing. After settling on this being the issue, it hasn't done it for the longest time...so, I can still put it off. Its difficult to trace the wire because they are encased.

Additionally, keep your tire air pressures equal and correct along with tires that are in similar condition - a difference in diameter will make a difference.
 

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Discussion Starter #17
Finally got the parts, tools, and time to tackle the problem today. Started with the driver's side because it seemed that's where the "scraping" sound was coming from. After getting the new harness soldered on and reattaching the wheel, I took it for a quick test drive before starting on the passenger's side. Lo and behold, the problem seems to be fixed!! Apparently no need to do the right side at this time. I've got the parts and tools so if that problem does happen again, I'll know what to do but it seems the problem is solved for now. Thanks so much to all of you for your help and advice!
 

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Great news. Definitely cheaper than replacing the transmission! ;-) Glad to hear that it was a cheap and easy fix. This problem is way too common on these cars.
 
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