(Realize I've searched this forum, YouTube and the 'net for 2+ hours to resolve the following)

Today, changed my daughter's 2005 G35's car battery. Came here first to research how-to. Followed instructions explicitly (thanks to the forum, btw), but when I connected the negative cable to the negative battery post, the horn blares intermittently.

Tried putting key in ignition / connected negative cable to negative battery post again, but received same loud result.

Am at my wits end. What am I missing?

Thank you for your time.

 

The factory alarm system goes off when the system senses one of the doors, hood or trunk open when the doors are locked.

The culprit is typically the sensor under the hood. Look for a plunger on the left fender well about 18 inches in front of the battery.

Disconnect the connector and see if the problem stops. If it does, you can insert a spacer to raise it up a half inch or so. Had a similar problem and this resolved it.

 

Wondered what that was for -.-

Nice to know someone can't steal my engine parts without setting it off.

 

The doors are unlocked and closed. Tried with key in ignition and when that didn't work, put the key in the driver's side door lock with it closed. Neither worked.

Found it. Thank you, but completely pushing the plunger down while trying to attach the negative cable to the battery post still results in the horn intermittently sounding.

I didn't disconnect it since pushing the plunger completely down with the hood open and attempting to reattach the negative cable to the battery post.

I suppose by simply pushing the plunger completely down to disengage the horns while one might be attempting to steal the battery wouldn't be much of a deterrent once car thieves new of the trick.

I succumbed to calling the dealership and asking for advice via a return call. We'll see how that goes and if they do respond with an answer I'll pass it along.

 

FINALLY got the correct method from dealership service.

After connecting the Positive cable to the Positive battery post, insert the ignition key in either the driver side door lock or passenger side door lock.

Connect the negative cable to the negative battery post, and the horn will start to blow intermittently.

Walk around to where the ignition key is in the door lock and turn the key as if locking or unlocking the door.

The horn ceases to blow. Whal-La ! It worked! Car started with no issues. Just reprogrammed the FOB.

 

Glad you got it solved

 

It was a fob issue. Good find OP.