rustybutterknife

Been lurking for a long while. I've learned alot from you guys already. I've been searching all over for the answer to this hoping someone will reckognise it. Thanks in advance. and Happy Thanksgiving.

wyoming9

iTrader: (1)

:jessica: That wire looks pretty rough maybe you should think of looking at it a little closer.

It does not matter where it goes as long as you have a good ground.

At one time it was up on one of the power steering bracket bolts.if it is the one I think it was..

I would think a good bolt on the block would be a good choice. Clean and never seize the threads your good to go

rustybutterknife

Trust me I know it's not the greatest. I'm just trying to get things put back as they should be (p.o. hacks) before I try tracking down problems that may not exist. I plan to do something with it (grease and shrink tube maybe) eventually. As far as I know I am getting good ground on the engine block and it seems to run ok without it hooked up. Guess I'm just one of those kinda guys that doesn't like the look of un hooked things in an engine compartment unless I know what they were meant to go to and am certian that they are no longer needed.

jerry507

I knew that I'd seen this exact part of the harness recently and was upset with myself for not knowing exactly where it goes. So I took a picture of it on my truck and it was a bit different than what I expected.



You would have noticed if you ran HAM or CB gear because the ignition coil would have made a racket on the RF bands. That little gray box bolted down is a noise filter and it won't do it's job right without the ground. Most of the sensitive signals (AFM etc) have independent grounds that run back to the ECU so you won't see any serious problems. You're probably overstressing the ground wires though. When Toyota laid out the harness they would have planned on currents heading back to the chassis at the specified points. If they're not there, current will have to travel back along other parts of the harness to a different ground which, when combined with what was designed to flow on those wires, may overload them. Eventually it will cause problems.

ksti

Mine is under one of the bolts that hold the coil/ignitor on.

However Wyoming is right it really doesn't matter as long as it's properly grounded.

wyoming9

iTrader: (1)

Please !!! explain How one can over stress a ground?? if one used perhaps to small of a wire.

All the metal of the vehicle is the ground unless it is insulated and isolated .

You have your various ground points on the vehicle where ever it was convenient to the vehicle being built .

it would not be practical but in theory you could ground every load to it`s own ground point

Or the opposite run every ground to one ground point now that would be a royal pain

Both these from a electrical stand point would work practical no.

jerry507

Ok, so there are two types of loads on most automotive and automotive-like systems (think construction equipment, off highway type stuff): pure loads like lights (things that simply draw power and it doesn't matter what quality it is) and sensitive types (sensors which are often things like ECT with one terminal tied to power).

On our trucks, and in every well designed system, the sensitive loads are typically grounded through the ECU with a dedicated return/ground wire. It's fine to use the same power wire as everything else because you can do all your filtering on the ground side t the same effect. But in general all wires will flow straight back to the ECU to keep a single common ground point at the ECU. In general, ALL of these types of loads are pretty low current/low power.

Before I talk about high power loads, it's important to know the electrical difference between ground at the ECU and ground at any random point on the body. Even straight from the factory there is resistance from ground point to ground point, and this will create voltage differences between those grounds. That's why all sensors (which are measured as voltages) are grounded back to the ECU to keep a level playing field. As time goes on though, all the various bonding surfaces get rusty/corroded and resistances go up. Wiring harnesses are affected a lot less by this aging, so are preferable to body ground connections. This corrosion actually gets worse if you're passing a lot of current, which is one reason why you never see headlight grounds go straight from bulb case to chassis, always with a wire to a decent quality lug point.

But everything else is a different story, usually high power/high current lights. In some cases, it's perfectly fine to use the body. The engine coolant SENDER is a good example. It's actually a current driven system and the block is pretty well grounded (if not you generally get a lot of other issues). In other cases like spark plugs there isn't a real good alternative. If it's a light, the quality of the power hardly matters. How the current flows from battery to light to chassis back to battery - hardly matters.

So now look at the harnesses and how they're designed. In the harness there is usually a complete ground path through the whole harness, even if it's periodically chassis grounded too. But those chassis grounds are places so high current loads only flow through a segment of the harness. A light for example, normally current goes from light ground to the nearest chassis lug. If that chassis lug isn't attached, it will still flow across the harness to another chassis lug. But that current will pass through conductors which are also returning (for example) alternator return current, EFI related currents, another light, ignition, whatever else. When Toyota looks at the harness, every wire is sized for the current it's EXPECTED to carry plus a factor of safety to account for extra load, aging etc etc. If you don't have the lugs attached properly you're riding on the factor of safety. Current was SUPPOSED to go to that lug but now it's flowing across a different part of the harness.

I did electrical design work for a time for a off highway manufacturer and the issues you run into get fairly silly. They actually did used to use the chassis ground a nearly exclusively for solenoid driven hydraulic valves, but they switched to using the harnesses for all return currents. The environment was pretty harsh and the paint would flake off, joint resistances would go way up and there would be apparent failures that were hard to track down. It was easier and cheaper to just replaces harnesses, which failed much less and weren't that much more expensive anyway.

It's also fun to look at the body electrical systems from front to back. The engine box is one welded piece, good electrical reliability over time. IIRC the rear lights have a ground wire running back to the cab because the body is really poorly grounded to the frame. Most serious HAM radio folks recommend adding 3-4 extra grounding straps to reduce interference issues from your bed. As a side note, the frame is all welded for the 4runner and it does use chassis ground for the rear lights.

More than you ever wanted to know about vehicle grounds

ksti

Wow, How did 1 freakin ground wire get so complicated?

wyoming9

iTrader: (1)

Seeing that your coming from the design side of things I can understand why you would think along these lines. Is a hard handicap to overcome.

In other words once someone has to put it mildly hacked a wiring harness it is pure luck the vehicle works at all

It is a moot point to each there own.

jerry507

Yea, I forgot to put in that it doesn't really matter where the lug goes. Just so long as the lug is on there. But it's sometimes difficult to see how something like this will cause problems 5-10 years later without the huge base of knowledge engineers have been developing over the decades.

No doubt there were at least a dozen people working on these harnesses to some degree or another