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Hello, this is my first post. I did search the forum and didn't find anything relevant in the first few pages.

Vehicle: 2007 TSX, 103k mi. Recently purchased for my son to use for college. Car is in great shape. New battery and alternator in last 3 months.

Problem: When decelerating, between 30-20 mph, the "Check Charging System" error appears in the central information display, and the battery light illuminates. This lasts only a few seconds at most.

Details: charging voltage is normal at idle, 14.3 V. I have checked the alternator plug, both battery cables, and the negative battery ground connection. All are tight and clean. And here is the interesting thing: the error message will only appear if the car is decelerating and IN GEAR (this is the 5AT). If I drop into neutral during deceleration, the error will not appear. And if decelerating in neutral, I can reproducibly trigger the error by dropping the tranny in Drive.

Any suggestions for how to trouble shoot this? I'm thinking that the issue is mechanical, either a faulty harness or ground connection, and triggered by the engine/transaxle torquing on the engine mounts during a downshift.

Thanks in advance!
 

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I ran into a random charging/battery light issue with my '06 6MT this past November. I dealt with it pretty quickly, so never established exact behavior patterns.

It went (and stayed) away after I cleaned up/re-torqued all of the ground connections (couple were sketch after 140k miles) and dielectric re-greased connectors suggested by my mechanic (coastal rains during winters). I since also swapped over to an Optima Yellowtop, which made an unrelated noticeable difference. Been peachy since ever since.

Good luck!
 

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It went (and stayed) away after I cleaned up/re-torqued all of the ground connections (couple were sketch after 140k miles) and dielectric re-greased connectors suggested by my mechanic (coastal rains during winters).

Good luck!
Much thanks for the reply. I am only aware of two ground connections--from the battery to the body, and from the block to the body on the other side of the engine. Are there more I should check?

Thanks!
 

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An update on this:

1) I located, removed, cleaned, and reinstalled all three grounding straps. All three were in great shape, and had very good metal-to-metal surfaces with no obvious oxidation.

2) I disconnected, wire-brushed, and reconnected both battery post cables. No corrosion, very clean, tight.

These steps did nothing to address the problem.

3) I bought a cigarette-lighter mounted digital voltmeter, and I can confirm that when the "Check Charging System" light comes on, the voltage drops to around 12.5, for a few seconds only. Then it bounces back up to 13.8-14.2, depending on rpm.

At this point I think I have one of two problems: 1) an intermittently faulty alternator, or 2) an intermittent connection on the wiring harness that runs from the alternator to the battery. The alternator is 3 months old, so unless it was bad at install I doubt that is the case. Anyone have any experience with the wiring harness?

Thanks!
 

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A bad alternator right out the box is not that unusual these days, especially if it is a rebuilt unit. Is it a new aftermarket, rebuilt, new OEM Acura? You might want to have some diagnostics run on it, if possible.
 

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Much thanks for the reply. I am only aware of two ground connections--from the battery to the body, and from the block to the body on the other side of the engine. Are there more I should check?

Thanks!
Sorry did not notice earlier...IIRK might had a lot more 2 connections...which now makes me think whether a prior owner put on a (crappy) grounding kit? Which would also make my case completely different :/

Never had an alternator fail at 3 months, but I won't disagree with Ken's point either. Re-manufactured and/or 3rd party/off-brand parts can be a gamble. I had a cheaper 3rd party alternative of a suspension top hat fail 2 miles from time of installation (bushings pulled through/disintegrated and the whole thing started clunking like crazy).
 

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An update on this:

1) I located, removed, cleaned, and reinstalled all three grounding straps. All three were in great shape, and had very good metal-to-metal surfaces with no obvious oxidation.

2) I disconnected, wire-brushed, and reconnected both battery post cables. No corrosion, very clean, tight.

These steps did nothing to address the problem.

3) I bought a cigarette-lighter mounted digital voltmeter, and I can confirm that when the "Check Charging System" light comes on, the voltage drops to around 12.5, for a few seconds only. Then it bounces back up to 13.8-14.2, depending on rpm.

At this point I think I have one of two problems: 1) an intermittently faulty alternator, or 2) an intermittent connection on the wiring harness that runs from the alternator to the battery. The alternator is 3 months old, so unless it was bad at install I doubt that is the case. Anyone have any experience with the wiring harness?

Thanks!
Hello,

I have the exact same issues. Did you ever solve this? I have changed my alternator once and battery for the third time.

Please let me know!

Many thanks,
 

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Hey, just fixed same issue. Unsure if you ever did. On my 'Starter Sub Wire Harness' that connects starter, alternator, fuse box and battery I found a loose connection. It is gray, 6 pins, and hidden under the manifold (near the starter). Shove your hands under there and try pressing the connectors fully in.

I also changed this wire for a brand new one. Unsure if I had to! Figured out issue once I made the same mistake putting the new one in and not connecting it back properly (semi common apparently).
 
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