Hello all, I recently purchased an 06 G35 6MT and have been fixing it up. Starting today, Only when idling I hear a loud occasional grinding noise coming from under the hood, along with an ABS light. I recently disconnected the Yaw sensor to fully disable traction control as I am planning to drift the car. I�m not sure if that could have anything to do with it but I have a couple other buddies with G35s that have done the same with no issues. At the same time as the ABS noise, the brake lights quit working. Not sure if that could correlate or if ironically the brake switch or bulbs went out. I am a Honda guy at heart and am still warming up to this platform, any help is appreciated.

 

You're probably hearing the ABS pump motor turning on. It will do a self-test the each time you start the engine and you hit 5mph, lasts about 1 full second but yes that pump motor makes a sort of grinding sound.

You're obviously having some sort of issue with the system though, I would start by inspecting the brake fluid level, that's the most common culprit for the brake light on. You can also scan it for codes with a code reader that handles chassis codes (starts with a letter C), most parts houses can do P, B, and C codes. There's a LOT of different reasons it can throw codes, lots of various sensors.

As for the brake lights, check the Fuse Box -J/B (cabin fuse box) to see if it blew fuse 20, it's a 10 amp fuse that is only for the brake lights. If so you probably have a short in the wire somewhere that needs to be fixed (trunk area is the usual culprit). Also inspect the switch on the brake pedal to make sure it didn't break off or anything like that. The chances of the lamp itself failing on both sides itself is pretty low, it's a ring of LED lights soldered onto a circuit board.

Malfunctioning brake light will screw with the VDC/ABS system as well.

 

You could unplug the harnesses from the ABS motor relay box to see if that sound goes away, you might have a stuck relay. It's that black box right in front of the brake master cylinder / abs valve block. iirc it has 3 harnesses plugged into it, unplug them all and see if the sound goes away.

Your instrumentation brake warning light will definitely be on with the relay unplugged.

 

I appreciate the help man. For the ABS issue, i decided to just fully disconnect it by cutting 2/3 wires on the ABS fusible link, and no more noise: I am using the car as a drift car so ABS doesn�t matter much to me. Now for the brake light issue, i was confident it could just be a malfunctioning switch but i replaced that today, still nothing. As well as both 10A fuses for the brake lights and taillights, still nothing. Running out of hope and options and am really hoping it�s not a wire issue.

 

Even if it's a wire issue it's not a big deal, on the brake switch is a pink / blue stripe wire. It goes directly to the tail light harness in the trunk, you can just cut/splice in a new wire if necessary.

Definitely pull the carpet, spare tire, and the plastic partitions out of the trunk so you can visually inspect for any obvious damage. All that stuff comes out EASILY and for a drift car you won't be using it anyways.

 

update: Found out once i replace the brake fuse, the brake lights work once then it blows the fuse. I am not at all the best with electric or wiring but will be looking for more info on this. Any help appreciated

 

Unplug the tail lights, put in a new fuse, tap the brakes. If it still blows the fuse then the taillights are NOT the issue. If the fuse holds then the tail lights are bad.

I suspect you'll find that the tail lights are fine, if so pull out everything in the trunk, carpet, spare tire, the plastic dividers, EVERYTHING, it's super easy btw.

Once you are down to the chassis metal and you can see the electronics for the stereo, the HICAS controller, etc you will be able to easily trace the wires from the tail lights until you find out where they rubbed against something and are touching metal.

Cut/splice to fix the damaged wire, or possibly just wrap in quality electrical tape like 3M Super 33+ or 35, if you can't find those then 3M Temflex 1700 would be sufficient. You can usually find one of those at Home Depot, Lowes, Ace Hardware, etc. Stay away from el cheapo crap wrap from Harbor Freight.

 

Update: I appreciate the help from everyone!! The brake lights turned out to be the rear defoggers shorting out. Unplugged them and the brake lights work fine. As for the ABS issue, I fully disconnected the ABS and i still occasionally get the griding noise behind the dash. I opened the hood to check for the noise and from under the hood its pretty much silent, can barely hear it, but its loud as hell when sitting in the car. Also sorta sounds like its coming from the passenger side. Is there anything I could disconnect to get the noise to go away? ABS is already disengaged as im using the car to drift and dont care for the ABS. Appreciate the help!

 

Weird, those are two completely different circuits.

Brake lights is fuse 20 in the cabin Fuse Block - J/B

Rear window defroster is fuse 8(primary heater power) and 12(control power) in Fuse Block - J/B as well as the relay on the back of that fuse block.

Glad you got it all figured out though, I suspect those two wires are grounded out against each other somewhere between the front of the car and the rear of the car.