Hey all! Long time lurker, first time poster.

Currently finishing a big 3 and alternator upgrade to serve a stupidly large sub ive installed in the cargo space. As part of the same overarching project im upgrading the sound deadening, fixing some leaks, and replacing the carpet. Im very inexperienced, so this has been a journey for me lol.

in the back of the car, where the ground goes from the battery to the chassis, the connecting bolt is on a sort of flap.



I cannot for the life of me loosen this bolt. I hit it with some wd-40 and i keep trying to loosen it slightly while supporting the flap, but im afraid of damaging the flap in some way. It flexes as i torque on the nut, and i dont feel i can generate enough force while supporting the flap to get it loose.

Once i can get this cable lug slipped over it the electrical work will be done! Any tips for a newbie like me?

 

Don't forget the sensor wrapped around the cable.
I got no advice on the bolt.

 

I appreciate any and all input, so thanks. Somehow i didnt even consider that sensor. Do we know what its for? I was looking at a forum post a while ago where people were discussing the fact that its there on some HHRs and not on others, i cant find that thread now though.

edit: i got curious, unplugging the sensor the car starts fine and doesnt immediately throw a code. Doesnt mean the sensor is unimportant but i was hoping to infer what its for lol

Edit 2: it sure looks like an amp meter. Might be a problem if thats critical to the ECU, my 2/0 will not pass through alongside the stock cable

 

Update: using the powers of speculation and mild inference, im going to run on the assumption that its a current sensor, used to help the ECU drive the alternator intelligently. Based on that assumption, im going to fly with the 2/0 not inside the sensor, monitoring the battery voltage and code reader under a sustained load to see if its a problem.

 

Just drill a 2nd hole in the flap and you’ll have a separate mounting point for your new cable.

Remember to scrap the paint to bare metal so you’ll have a good ground.

 

seems rather obvious in hindsight. Thanks!

 

Yes, it is a current sensor that activates the voltage regulator that is firmware. It is very important.

 

well shucks. Im not quite sure what to do then. Maybe i follow that advice to drill a second stud, pull the oem from the sensor and connect it to the new stud, and have my 2/0 OFC take its place. Not a fix, but since the 2/0 should carry most of the load that would probably be better.

The only other thing i can think is going crazy on EE, figure out how the sensor signals the ECU, and somehow swap that out. The 2/0 simply wont fit alongside the factory cable, and id imagine the reading would be innacurate even if i did shove it in there since both cables would be off center...

 

You could connect your new cable to the stud and nut that's on the post clamp. Then all energy will flow through the current sensor.

 

Thanks to everyone who replied, and the moderators for keeping this forum running, its been endlessly helpful.

Some AeroKroil got it off no problem, and i realized i dont actually need the stock cable. Everywhere else ive run my big 3 in parallel with it, so technically this ground is under-powered for the rest of the system, but:

i think 2 gauge maxes at 130 amp, im sure the stock car didnt pull that. My subwoofers average (inferring from Wrms) 187.5 amps at max, and this ofc is rated for 300-400+ amps on its own from what i see. Max my car could ever pull sustained, as i understand it, is around 317 amps.

So, once i accepted that the stock cable was unnecessary, threading my 2/0 through the now empty sensor and taping it like the stock cable was trivial. I present the dinkiest cable to ever cable:



ECU should now see all the current. How'd i do?