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So, we left the key in the on position by mistake for about 2 hours on our 2011 MDX with 46,000 miles and original battery. Batt went dead. Jumped with another car per the MDX book. Took it for a ride to recharge. Noticed it was rpm-limited at 3,000 rpm's. Back at the ranch, turned it off, restarted fine but 4 warnings in info displayed showed up: Emissions, AWD, VSA and TSA. Plus, when restarted, after about a minute at normal idle, it automatically revved up to 2,000 rpm's--and stayed there. Any similar experience out there ? Thanks.
 

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I think the ECU would need to reset and re-learn; but, it shouldn't show all those warning lights or rpm revs. I had my alternator go out on my RDX last year and it gave me the same type of warning lights (I had no rpm revs). The alternator wasn't putting out enough voltage and it was stealing it from the battery until the voltage was too low run the vehicle. Maybe the MDX is revving the engine to charge the system (not sure if the MDX is smart enough to do this at idle).

The OEM batteries are not the best, it might be worth checking out your entire electrical system. You can also get a battery charger/maintainer for about $50-$75 at autozone to make sure the battery is topped off. I've noticed if you completely drain a battery, they never seem to come back 100%. Most places can do a free test to make sure the battery is A-OK and just needs a complete charge. Modern cars don't like to drive with low voltage. Both my MDX and RDX give all kinds of warnings like you had when voltage is low.
 

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So, we left the key in the on position by mistake for about 2 hours on our 2011 MDX with 46,000 miles and original battery. Batt went dead. Jumped with another car per the MDX book. Took it for a ride to recharge. Noticed it was rpm-limited at 3,000 rpm's. Back at the ranch, turned it off, restarted fine but 4 warnings in info displayed showed up: Emissions, AWD, VSA and TSA. Plus, when restarted, after about a minute at normal idle, it automatically revved up to 2,000 rpm's--and stayed there. Any similar experience out there ? Thanks.
So you have about 5 years on the original battery, and you discharged it completely by accident.

I think you need a new battery before this dead one shorts out your alternator.

It's always a bad idea to run the car to recharge a depleted battery. I can think of no better way to kill your alternator.
 

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Thanks mrgold35 and newmdxowner. Did not know damage to alt could result from trying to charge a low battery by driving it. That's how my dad did it way back when. I'm just hoping I didn't fry something while trying to connect last negative cable to the specified spot on the engine by touching some other metallic part of the body. This car has been absolutely perfect until running down the battery, no sign of even a low battery due to any alt issues. Have appt at Acura dealer next week. I'll let you guys know what and how much $$$ ! Thanks again
 

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Acura dealer replaced ECM under warranty, problem solved. Electrical system checked out fine. Used to get some pinging when AC on under acceleration with 87 gas. Now, not a sound. I'm thinking ECM was not monitoring all aspects of engine accurately. Running much more smoothly now, night and day. Thanks for your input.
 

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That is good news! Good thing you found this out before the warranty ran out. My out of pocket repair cost is about 5%-10% of what they could have been between basic, powertrain, and extended TSB Acura warranties on all 3 vehicles.

One of the main reasons I like longer warranties with (near) luxury brands compared to non-luxury brands.
 
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