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Discussion Starter #1
Please save your judgement about exceeding 100mph, I just need ideas on the cause of this, it's not a good thing to lose my AWD system when exceeding 100mph. The vehicle does indeed only operate in FWD mode until I turn the car off and back on again, then AWD works as normal. Any ideas on how to troubleshoot this or prevent it from happening again (while still maintaining my ability to exceed 100mph)? Thanks
 

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So it gives you the sh-awd warning only when you take it past 100? Did it just start doing it? Also has it happened under any other circumstances? I'm taking a wild guess here so don't hold me to it, but maybe its a wheel speed sensor? Another wild guess is maybe your rear diff is getting pretty hot during these 100+ mph runs but the speed sensor seems much more logical to me.

I've taken mine past 100 a few times and no warnings or anything like that has ever happened, still feels solid.
 

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Does SH-AWD even works beyond those speeds? Never gave it a thought.
 

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There were times I've set the cruise control at 90 mph and touched 100-105 mph when I needed to pass in a hurry. I only touch +100 mph just to drop back down to 85-90 mph. The hwy from El Paso to San Antonio is 80 mph and 90 mph seems to be the minimum speed. I didn't notice any warning light when +100 mph. I never set the cruise control or did sustained driving at triple digit speeds.

How long/miles are you sustaining +100 mph? Do you always get the warning every single time. Did the issue just started recently? How soon do you get the warning once you break 100 mph? Have you checked out any codes to see if it is sensor and/or overheating sh-awd related?
 

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Does SH-AWD even works beyond those speeds? Never gave it a thought.
It does, but by 100 or so I've noticed (on the MID) it drops to 1 bar being sent to the back.

Like @mrgold35 said, I don't stay at 100 mph very long, tops of 2 minutes. I only do it on long open stretches. There was once where I really pushed it to see how far the mdx could go, and that was to about 115 mph. Its pretty gutless up there and I didn't want to push my luck so I let off and coasted back down to 80 or so.
 

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I have been over those speeds myself and also didn´t got any warning lights.. Top Speed I could reach was the logical governor of about 130mph, You can feel the engine basically not pushing it anymore like it cuts-off fuel at the RPM and Speed combo of 130mph because there was no force beyond that even on a down hill grade.. The MDX should push at least 140-150 on itself but obviously taking its god damn time after 120mph to 150 IF it wasn´t governed.
 

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Discussion Starter #7
So it gives you the sh-awd warning only when you take it past 100? Did it just start doing it? Also has it happened under any other circumstances? I'm taking a wild guess here so don't hold me to it, but maybe its a wheel speed sensor? Another wild guess is maybe your rear diff is getting pretty hot during these 100+ mph runs but the speed sensor seems much more logical to me.

I've taken mine past 100 a few times and no warnings or anything like that has ever happened, still feels solid.
That's exactly what my mechanic friend said, wheel speed sensor. Diff shouldn't have been too hot, brief drive and a quick trip up to 100. No it only comes on when I exceed 100-110mph. He said we'd have to hook it up to some machine and take it up to that speed to troubleshoot this issue, guess I'll roll with that advice. Many thanks!
 

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Discussion Starter #8
It does, but by 100 or so I've noticed (on the MID) it drops to 1 bar being sent to the back.

Like @mrgold35 said, I don't stay at 100 mph very long, tops of 2 minutes. I only do it on long open stretches. There was once where I really pushed it to see how far the mdx could go, and that was to about 115 mph. Its pretty gutless up there and I didn't want to push my luck so I let off and coasted back down to 80 or so.
Mine does not feel gutless at all at those speeds. Just scares me when I lose my AWD.... Perhaps you were hitting the governor?
 

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Mine does not feel gutless at all at those speeds. Just scares me when I lose my AWD.... Perhaps you were hitting the governor?
I don't believe it was the governor. When I took it up to 115 it was back during August and since I live here in florida its pretty hot year round, but even more so in august. I also seem to think it was a slight uphill grade but I can't be sure. I will say though that it reaches 100+ very easily, nothing like my 2011 honda accord. That thing takes forever just to even get close to 100!

If I get a chance in the upcoming months I'll try to push it again since its finally cooler now and I don't need to worry about snow or anything like that haha. Hopefully the speed sensor is your problem, those are pretty cheap and easy to replace.
 

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Update: when the engine is ice cold and temps are in the 30's, I can pull to 105 or so with no AWD failure light emitting. So it does seem to be exacerbated by heat. I do remember one other very long drive during summer, where I pushed it to 100 on a slight incline, and the AWD failure light came on either right at, or just below 100mph. So heat + long drive + pushing past 100-110mph is pretty much guaranteed to trigger the AWD system failure message in my experience. I'll get with my mechanic after the holidays to do some tests to determine the cause, likely the speed sensor as another poster suggested. Note, when this light is emitted, it's definitely in FWD mode, the front tires chirp at nearly every light. I do have a lead foot........ AVG MPG 16.9 per the cars determination. I admit, I drive like a bat outta hell, safely. Don't hate, I just push my cars pretty hard. It's held up nicely.
 

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Update: when the engine is ice cold and temps are in the 30's, I can pull to 105 or so with no AWD failure light emitting. So it does seem to be exacerbated by heat. I do remember one other very long drive during summer, where I pushed it to 100 on a slight incline, and the AWD failure light came on either right at, or just below 100mph. So heat + long drive + pushing past 100-110mph is pretty much guaranteed to trigger the AWD system failure message in my experience. I'll get with my mechanic after the holidays to do some tests to determine the cause, likely the speed sensor as another poster suggested. Note, when this light is emitted, it's definitely in FWD mode, the front tires chirp at nearly every light. I do have a lead foot........ AVG MPG 16.9 per the cars determination. I admit, I drive like a bat outta hell, safely. Don't hate, I just push my cars pretty hard. It's held up nicely.
running the same tires on all 4 wheels? How old are the tires? Same age or different ages? When is the last time the rear diff fluid was replaced? Center Diff? When the CEL/AWD error comes up, does it display a code? Have you tried to use an OBDII scanner to get a code?
 

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likely the speed sensor as another poster suggested. Note, when this light is emitted, it's definitely in FWD mode, the front tires chirp at nearly every light.
This description def points to a wheel speed sensor on it's way out. Do you have snow where you live and does your car have a lot of corrosion? Let us know if it ends up being the passenger rear wheel speed sensor.

Also, does any lights come on or does any codes get stored when this is triggered?
 
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