Disconnected negative battery terminal, car won’t turn on anymore.

tacthecat

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If car cranks (at a reasonable speed) but doesn't start the battery is fine. Look elsewhere.
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stevebinh

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That happened to me when I put in my sub and amp, it was a starter fuse under the hood a blue one. Check that
 

stevebinh

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Also the battery has been good enough to run my amp and sun, it’s been about half a year now since I installed mine. So you or battery should be good, I just know after installing mine a fuse blew so I would check that
 

ACUITY

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2018 civic sport touring. Was adding an amp and sub into my car. Was working totally fine and the car was starting. I disconnected it again to re do some wires for the sub and when I turn it back on all of my safety systems have problems and my car will crank but won’t start. The infotainment screen will turn on for a second but will turn off quickly. I don’t know what’s going on.

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Probably a stupid question...but are you missing the nut that goes on the negative terminal to actually tighten the terminal to the battery post? I don't see the nut in this image, and if it's missing, the terminal is loose on the battery and possibly making a bad connection. If that's missing, replace it, tighten the terminal and give it another go.

The comments about the battery not having tons of charge because it's small and not being able to work with the car off long are fairly accurate. If you can believe it, the civic battery hasn't changed in a few generations despite the higher power load on the electrical system of modern cars.

Here's an image from one of our install guides showing the nut I referenced:
Honda Civic 10th gen Disconnected negative battery terminal, car won’t turn on anymore. 1611593335799
 

Deane

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If the engine is cranking (turning over) smoothly that means the battery must be fine because cranking is the biggest load test you can do!
 


calonzo

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Probably a stupid question...but are you missing the nut that goes on the negative terminal to actually tighten the terminal to the battery post? I don't see the nut in this image, and if it's missing, the terminal is loose on the battery and possibly making a bad connection. If that's missing, replace it, tighten the terminal and give it another go.
Good eyes!
 

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When I disconnected my battery and tried starting the car using only the clutch it would actually start but quit within a second or two. It started about 5 times in a row until I clued in on the message in the instrument cluster "brake and clutch"

However the OP clearly has a CVT so that isn't the issue.
 

flapz

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In the not too distant /olden days /beginning with the dawn of auto electronic brains, disconnecting the 12 volt battery source without an alternate parallel source of at least 9vdc hooked up would result in various nefarious electrical symptoms including confusing smog compliance monitoring devices (check eng light) . Since auto cigarette lighters are now seldom seen, I'm forced to now hook up my emergency start lithium power supply when ever changing a battery or taking it out of the circuit.
And the lady is right, battery terminations can easily go high resistance but removing either termination to clean it without providing the parallel supply can possibly result in the same negative results.
My 1965 Ford F100 never has this issue and it can barely spell smog but our 2017 Civic has electronic everything.
 
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kanyeasasda

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Probably a stupid question...but are you missing the nut that goes on the negative terminal to actually tighten the terminal to the battery post? I don't see the nut in this image, and if it's missing, the terminal is loose on the battery and possibly making a bad connection. If that's missing, replace it, tighten the terminal and give it another go.

The comments about the battery not having tons of charge because it's small and not being able to work with the car off long are fairly accurate. If you can believe it, the civic battery hasn't changed in a few generations despite the higher power load on the electrical system of modern cars.

Here's an image from one of our install guides showing the nut I referenced:
1611593335799.png
Oh yea, I am! I totally forgot that I dropped it and lost it. I will try to go buy a new one, is it a 10mm hex nut?
 


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kanyeasasda

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Also the battery has been good enough to run my amp and sun, it’s been about half a year now since I installed mine. So you or battery should be good, I just know after installing mine a fuse blew so I would check that
Ok I will definitely take a look at that. Thank you!
 

SDzx

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Could have grounded it somewhere on accident and blew a fuse. Happened to me when installing my audio system. My fuse was in the engine bay, but my problem was with the radio. Good luck!
 

pinhead

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Whevever I have to disconnect one or both battery terminals, I wrap a plastic bag around the terminal end and hold it on with a rubber band. Eliminates the chance of grounding something out and damaging something. Modern cars are hideously vulnerable due to the sensitive electronics all over the place.
 

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Oh yea, I am! I totally forgot that I dropped it and lost it. I will try to go buy a new one, is it a 10mm hex nut?
It does use a 10mm socket, but I am not sure if it is a standard M6x1 nut or something more specialized. I suggest you see if a local Honda parts department has one or can at least advise exactly what you should use as a replacement.

~Russ
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