Most of what you said is true but you are not seeing the value of the DRB3 or any other scanner. It is correct that it is only a tool but tools are what it takes to get the job done; in this case diagnose an intermittent no-start condition. The DRB3 is all I use at home on my cars.
Mechanics rarely test parts. I worked with a very ineffective teacher who put great stock in teaching how to test parts because that is what he understood. He never was a mechanic. He was a service adviser and was not qualified to teach what he was teaching. The level of dissatisfaction among students and employers was very high. Time is money, both for employers and customers. I saw one fellow get fired for "testing" a thermostat in a can of water after the new one took care of the problem. (That wasted an hour of the boss's time but it was not his first offense). Good mechanics diagnose as quickly as possible, then replace parts. They understand that replacing random parts introduces new variables that computers are not ready to relearn and can affect performance, and they know that testing of parts wastes time and to be effective in finding the cause of an intermittent problem, it must be done while that part is still in its bad state. In the case of your ASD relay suggestion, no testing is involved and no parts need to be purchased. Simply switch it with a different one like it such as the AC compressor relay or wiper relay. If the problem still occurs, you can move on to in-depth testing without wondering if that relay is all that is wrong.
There is little chance anyone will be successful replacing a spark plug without a spark plug socket, but it can be done. There is little chance you can remove a trim screw without a screwdriver, but it can be done. There is little chance you can diagnose a no-start problem without a scanner, but it can be done, if you want to waste a lot of time. In all those cases you need the right tool for the job. You are right that the DRB3 is just a tool, but it is the right tool for the job.
To identify an intermittent ASD relay which is extremely rare, you might check for spark when the no-start condition pops up. You might also observe that the fuel pump does not hum for one second after turning on the ignition switch. But you still do not know if it is a defective relay, a defect in the computer running that relay, a wiring problem with the relay's coil circuit, or the most common cause, an overheated contact or connector terminal on the ignition switch. You would need to drag out your voltmeter or test light to test all those circuits with a helper, or, all of those things can be learned in less than a minute with a scanner. The DRB3 lists the ASD relay and whether the computer has commanded it on or off. It also lists "ASD Sense" meaning did the relay actually turn on and send twelve volts to the ignition coil, fuel pump, injectors, alternator field, oxygen sensor heaters, and back to the computer? If it is listed as "high", you instantly know every circuit associated with the relay, and the cam and crank sensors are working. It lists "twelve volt ignition sense". If that is "high", you know the ignition switch is working. Without that proper tool, how long would it take to test all those circuits before you found the one that needed further diagnosis?
Most aftermarket scanners today do a real good job but they never do everything the manufacturer's scanner will do. In some cases they do more, such as tell you which wire color to test and what to expect, but I never allowed my students to use them, or the troubleshooting charts in service manuals. Both of those tools are for people who do not understand the circuits they're working in. That does not mean those people are stupid or unqualified. It just means they have not learned the circuit yet. You can be the best over-the-road driver in the world, but occasionally you may need a road map because you do not have every route memorized. When my students truly understand how a circuit works, the diagram is all they need to know what to test and the results to expect, but they still need the tools. In many cases a voltmeter is that tool. When testing numerous parameters of a circuit that a computer already knows, the most effective tool to use is one that can talk back and forth with that computer, and that is the scanner.
If you could measure a good signal from a cam sensor, then from a crank sensor, how are you ever going to determine if they are in sync without a scanner displaying that information from the computer? Worse yet, if the cruise control kicks out intermittently but can be "resumed" a few seconds later, how will you ever find that without the scanner to display "reason for last cutout"?
You are down-playing the importance of the DRB3 being the right tool for the job. You stated it is not thorough with all engine problems. We are not dealing with all engine problems; we know we are dealing with an electrical or fuel supply problem, and based on the really good description of the symptoms, we can rule out fuel problems. Mechanical problems will not cause a sudden stalling and intermittent no-start, then magically fix themselves later.
"It also happens offen that mechanics request to change this part and that part, and yet another part, all without throughly testing the parts they want replaced, making the owner spend lots of hard earned dollars, to no avail."
You have that backward. It is do-it-yourselfers who throw random parts at a problem in hopes they will stumble on the fix. One of the goals of this forum is to prevent people from doing that and to straighten them out after they have done it and are still lost. Every time a mechanic wants to simply "try" a part, unless it is something they normally stock, he has to order it, wait for it to arrive, then when it does not solve the problem, it gets put in stock and represents wasted money. It could be years before that part is sold, if ever. Worse yet, with intermittent problems like this, how do you know that new part is the solution? We know it is not the solution if the problem occurs again, but what if that problem does not occur in the next week, or month? Is it fixed? Would you trust it on a trip deep into the wilderness?
The other thing you are overlooking with scanners is their ability to record a snapshot of events occurring with input sensors telling the computer how to respond and output sensors telling the computer the results of that response. We are lucky here that the vehicle stalls and remains in the no-start condition for half an hour, but what if you do not get your testing done in that half hour? The clues to this problem can be captured in a few seconds of sensor data, but only with a scanner with that capability.
You would be hard-pressed to suggest a better tool for finding this problem, but a lot of testing has already been done on this vehicle. We are way beyond the simple and common stuff. Now we are looking for the more obscure, one-of-a-kind, uncommon causes. The chances of stumbling onto a corroded connector terminal or cut wire are very small so we have to rely on more involved test results and observations. That is pretty hard to do over a computer, so the best we can do is suggest the best course of action that will help the mechanic and/or owner resolve this. We need to make that process as simple and reliable as possible. That is by using a scanner, even if it must be rented or the vehicle must be taken to a mechanic.
Tuesday, June 26th, 2012 AT 6:43 PM
