I'm tired of wiring testing being my achilles heel when working on cars. Here's a couple of questions I have, and I know they are noobish, but I've actually worked on my 97 Z for 9 years now.

1. When a diagnostic says "check for hot", how exactly do you do that? For instance, With KOEO, check for hot at the pink wire at the ign coil. Do I use a test light and ground the negative to the battery and then probe the pink wire? Or am I using a multimeter looking for a specific voltage or amperage?

2. How do I test wire sections? I know it's not common for a wire to be damaged internally without the outside being severed, but just in case it ever happens, how could I test, say, 6 inch to 1 foot sections of wire at a time for continuity?

I may add to this later, but this should suffice for now. Thanks guys!

 

To check "KOEO" voltage, hook the + (red) side of a multi meter (set on DC volts) to the pink (or whatever color wire you are working with) wire, and the - (black) side of the meter to any chassis or engine ground. Should read battery voltage, typically 12+ volts (or 5V for many circuits originating in the PCM). You are only interested in volts at this point, not amperage.

To check a wire for a break, hook one lead of the multi meter (set on ohms) to each end of the wire you want to test. Resistance should be close to "0". It the wire is broken internally, the meter will read "infinite" ohms = open circuit. If you get infinite ohms, keeping one of the meter clips on the end of the wire, attach the other lead to a straight pin, and puncture the insulation at the middle of the wire and measure ohms again. That will help you determine which 1/2 of the wire has the "open". On that section, move the pin to the middle of that section, now you have identified the 1/4 of the wire that has the open. Keep going until you narrow it down to the specific section of the wire that has the break. To be practical, if you find a wire that has a break in it, replace the entire wire rather than trying to pin down the exact point where the break occured and splicing it. Often the breaks are at the pigtail end, so thats the best place to start.

 

Another thing to remember when checking continuity on a wire is to always make sure there is no voltage present. Voltage will make your reading meaningless and may damage your meter.

If you are unsure, check for voltage first, then do your resistance check (or "ohm it out" as many say).

Before you test for resistance touch your meter leads together and see what the ohm reading is. If it is not zero, subtract that reading from your actual reading of the wire under test. Older meters normally had a way to zero out the ohm reading when the leads were touched. Modern digital meters (which you should be using) not so much.

 

These are two basic tests that will help you track down problems. Your first question about "testing for hot", means more or less what you already think it does. Power at the wire. If there isn't a specific voltage, then it's usually safe to figure that it means battery voltage. Hook the black test lead to the neg. bat. terminal, or a good ground and test with the red test lead.
A word of caution. When working on a computerized vehicle, it's recommended that you us a high impedence volt meter and not a test light. In plain english, it's a digital meter, not the kind with a needle that sweeps. Digital meters don't "load" the circuit when connected like a test light or an old school meter will. The extra load can damage components in the system causing more harm than good. That's not to say never use a test light. They are great for diagnosing tail lights, power windows and non computerized stuff.
Your second question deals with continuity. One of the functions of most digital meters is an ohm meter. Many also have continuity as well, but I prefer to mostly use the ohm meter.
A continuity tester will usually have an audible beep that will sound if you touch the two leads together. That indicates a circuit or connection. Break the circuit and you won't get a beep. This goes for six inches of wire or from one end if the car to the other. Think of it as an audible test light. It will tell you if there's a pretty good connection, or circuit, but it doesn't put a value on it. It either beeps or nothing. That's great especially in situations where you have to crawl up under the dash and try to test wires you can barely reach. Trying to do that, while looking at a meter can be impossible.
An ohm meter reads resistance. A prefect connection will read zero or almost zero. Most meters don't read zero even when you touch the test leads together. No connection or "open circuit" will read higher than the meter can read and will usually be a blank screen or OL(out of limits). Anything in between will be read as ohms or restistance. This can be usefull at times because it can make you aware of a problem or potential problem, that the others won't. That also doesn't mean that you will get all the answers from testing with an ohm meter. It has limits like everything else and should be considered a tool for diagnosis and not the answer to all your prayers.
One more thing. Always try to test wires at connections if you can. Don't pierce the insulation on the wire just to test unless there's no other way to connect. You can use paper clips to back probe connectors. That's when you slide the paper clip wire along the wire into the back side of a connector. If you can get it in there far enough, it will touch the metel of the ternimal that's connected to the wire. It's far better than poking holes all over the place in the insulation. Each one of those holes is a potential place for water to get in and cause you trouble.
This stuff takes patience and time, but it's worth learning because there's only so much you can do without it.

 

Thanks a ton guys. That should at least get me on my way. Testing a no start condition right now on my GFs 95 TA, and since I can't scan codes without going through the hassle of buying an OBDI scanner and buying or making my own adapter for the 16 pin, I'm doing this the old fashioned way. Got spark from the coil to the end of a screwdriver today, so I'll be going down the list of the "No Start Diagnostic" on mainstreamtopics tomorrow, starting with the opti. She just blew a heater hose down near the opti and lost all her coolant, and I fear it has prematurely ended the poor distributor's life.