I mounted mine on the ledge by the firewall on the passenger side. That way I could bring it in through and get the mutual grounding over there where I plug in the additional port thingee of the Pro part.

While I was in my dash this weekend I put in a couple relays. One for the inter-cooler flow light so that it comes on when there is no flow instead of when there is flow, and another for switched power for the wide-band. Trent found some 4' extensions for the wide-band connectors, I should be able to cut one and run it through the firewall, then solder it back together at the right length. Then just plug or unplug the two sides in when you need them.

Be careful on that guys. There'* a possible grounding issue. The wideband and whatever is reading it needs a common ground. (maybe I'm thinking of Aeroforce) but there'* something in the directions about power and grounding potential issues that lead to readings being off.

The control unit and the gauge need to be a separate ground if I remember right.

It could have something to do with varying voltages since power starts at the negative end and flows out the positive... I have a common ground for everything on some hefty wire so that shouldn't be an issue, although I may need to split them off onto their own ground with a ground loop isolator depending on the amount of noise they introduce into the system. The heating of the sensor has been known to cause some bad whine in the speakers. The aeroforce is powered off of OBD so I doubt that is what your thinking of.

Someone grab the pdf of the instructions and see which it is. I used a common ground buss to ensure they were all on the same

I think it might be the heater ground that needs to be separate.

2.3 Electrical Grounding Concerns

The electrical environment inside a car provides unique challenges, combining high voltages and currents, low-voltage signals, convoluted signal paths, and variable conditions (i.e., fans turning on and off, or starter cranking). When using precision electronics, it is important for ALL electronics to share a common ground. Remember that “Ground” is more than just the return path for any circuit- it is also the reference against which any voltage is measured. Since it is not always practical to ground every device to the exact same location, here are some tips on grounding:

1. The BEST grounding scheme is all grounds (i.e., ECU, Gauges, LC1 heater, LC1
system, etc.) SOLDERED into a single lug and bolted to the engine block.

2. The next best is all grounds attached to the same source, as close as possible, but on
separate lugs. This is because even the corrosion between lugs can create ground
offset and noise. Incidentally, this is why many ECUs have separate ground wires for
injectors vs. ECU system ground- separating high voltages and low voltages reduces
noise.

3. Grounding to the engine block is usually better than grounding to the frame.

4. Grounding a gauge to the radio is usually bad- ground offset can vary with volume.

5. Grounding to an ECU housing is generally not optimal- housings are strapped to the
frame for shielding, but not necessarily grounded.

6. One of the WORST things to do is to ground most of your electronics to one place (i.e.
the engine block), but ground one device somewhere else (i.e., the frame). Not only can
this result in ground offsets, it can also create a “path of least resistance” for high
currents THROUGH a low-current device. This can result in melted wires and vaporized
diodes, when, for example, starter currents flow through gauges.

That'* been changed then. My instructions said not to put the heater ground with the others.

That'* from the "1.9 – 8/23/07" version. Looks like they did a lot of updates to it. Looks like that is the newest version though. That leads me to question where the ECU is grounded to, sounds like I need to find good bolt near the firewall and clean it up. I don't know about soldering the wires to the bolt... I think a good sized ring terminal with the wires soldered to it should be sufficient. I'll just run a ground in for the inside gauge with the rest of the wires.