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Magnetic shock absorbers stiff

Tiny
DWBRITTON
  • MEMBER
  • 2016 GMC YUKON
  • 6.2L
  • V8
  • 85,000 MILES
The vehicle ride suddenly turned bumpy and bouncy as if the front end shocks were bad. It has MRC shocks. The front end (both sides) seem very stiff compared to the back. I was told that they may have “locked up”.

How can they lock up and what would cause them to lock up?

The other thing that coincides with this was a recall for loss of braking vacuum firmware update.
This problem became noticeable & showed up after the GMC dealer update.

If they are locked up, is there a solution other than to replace them?
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Saturday, May 2nd, 2020 AT 6:52 PM

8 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
If both sides failed at the same time then it is unlikely that the shocks themselves failed. It can happen but is not likely. Basically these are independent components and for them to fail at the same time is highly unlikely. The fact that both of them are controlled by a singular module, I would look at the module as the issue. Also, it is most likely a faulty sensor or other input to the module to make it think that the more firm setting of the shocks is needed.

I included all the info about this system for your review. Let me know what questions you have.

As for the recall being related, that is very unlikely. If this were causing a problem it would be well documented because they have done tens of thousands of those recalls and I don't see any other documented complaints of this happening after the recall.

As for how to figure this out, we need to find out what the input sensors to the module are telling it to find out if there is an issue. The only way to do that is monitor it with a scan tool that can look at this live data.

Let me know what questions you have and we can go from there. Thanks
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Sunday, May 3rd, 2020 AT 9:29 AM
Tiny
DWBRITTON
  • MEMBER
  • 5 POSTS
Anybody home? This is the forth time to try to follow up on your answer and info.
Did you see the additional info I supplied?
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Friday, May 8th, 2020 AT 10:26 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
4th time? I only see the once. Anyway lets start by checking the fuses (RSE, RTD, ICCM, etc) here it a guide to help you with the suspension wiring diagrams so you can see how the system works with the fuse locations as well:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Saturday, May 9th, 2020 AT 12:18 PM
Tiny
DWBRITTON
  • MEMBER
  • 5 POSTS
I’m not sure why my 2 previous replies didn’t go in.
I don’t believe the issue is electrical. The shocks as reported by 2 different technicians are “locked up”. No dash alert.
I removed the electrical connections to both shocks. Drove it, bounced it. No difference in performance. Got dash alert. Both shocks extremely stiff with or without power.

If the shock control module were out or a fuse blown(?) Why don’t I get a warning like I did when the shocks were dis connected?
If the shock control module is out or fuse blown, wouldn’t the rear shocks act the same? (They don’t, but rather like a shock with give with the engine off.

Back to the original question, how can these shocks lock up? How to unlock them?

What does the industry have to say regarding the lockup? How prevalent is it by your resources?
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Sunday, May 10th, 2020 AT 10:18 PM
Tiny
DWBRITTON
  • MEMBER
  • 5 POSTS
I’m reviewing the schematics as well and will check for a fuse problem. As I said, it doesn’t follow for a dash indicator when disconnected and none when connected.
Thanks for your input.
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Sunday, May 10th, 2020 AT 10:38 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
The shocks should not be stiff with the electrical disconnected. It must be one shock that is locked up causing it to seem like both. lets remove the shocks to confirm here are instructions in the diagrams below. This video shows how to remove the shock and spring on a similar car which the process is the same:

https://youtu.be/sug_NoHfXG0

Check out the diagrams (below). Please let us know what happens.
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Monday, May 11th, 2020 AT 11:14 AM
Tiny
DWBRITTON
  • MEMBER
  • 5 POSTS
GM is footing part of the cost through GMC dealer to replace both units.
Both the units are rigid. You cannot get motion In the front that is at all similar to the back when bouncing it.

I am hoping I can retain the parts.
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Monday, May 11th, 2020 AT 12:15 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Thanks for the update. That is great info. Unfortunately if they are covering them then they will most likely return the parts to GM. Let us know if you have more questions. Thanks for using 2CarPros.
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Monday, May 11th, 2020 AT 7:40 PM

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