I have a battery relocation that I belive is making my Megasquirt mort complicated than it is worth. The battery relocation has a 6 ga wire going from the positive of the battery to a powerblock in the engine compartment. The engine and negative battery terminal are grounded to the frame. The MS main power/fuel circuit relay is on a chasis ground next to the front strut. All of my sensor grounds are gounded out on the part of the firewall that extends out to allow for water to collect from the windshield. I was having problems with the stock ECU making loud pitched ringing when I had the sensor relay grounds sharing a ground on my valve cover that was also connected to the frame with a 6 quage wire. Even though the ECU was making new the MS computer came on sometimes. Now I have the current configuration the MS doesn't come on at all.

Any ideas?

I went though the grounding again and found that I combined both grounds from the MS to the same ground as the sensors (4 wires).

I now realize that thse should be seperate from each other and the sensor grounds.

Should I run a negative wire from the battery for both or do one chassis and one negative? Both chassis?

I relocated my battery to the trunk. I ran a 4 awg ground to the front so that those things can be grounded "directly to the battery".

Don't run your MS ground through the chassis, that's just asking for trouble.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

Roger that

I will run a ground wire to a ground block for all the MS grounds. Is it ok for the relay ground to share the ground block?

In my setup, each sensor for the MS using the ground in the factory harness for the corresponding factory sensor. So basically my MS IAT shares a ground with the factory IAT. NO problems.

My MS grounds are connected to random screws under my center console and the ones for the sensors are connected to the nearest bolt (one on the firewall and one on the passenger side fender) and I havn't had problems.

Evo 8 - 12.3@113 circa 2009 (~330whp)
Now with BB Xona Rotor HTZ FP Red and ~450whp
2018 MSM Civic SI Ktuner TSP stage 1 w/ Honda hacked headunit.

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2012 2500HD LML

I am still having issues even though I ran wires straight from the negative terminal. My issues probably are elsewhere.