Training for the Future

By Dave Hobbs. “Hybrid vehicle electronics are dangerous and only the dealerships will be able work on them.” “The independent garage is on its way out.” Have you heard statements like these before? I have, and I have to disagree with these opinions, based in part on history.

Let’s turn back the clock for a moment. It’s the 1960s and generators are replaced with alternators. A gloomy future is predicted for independent repair shops. My dad, Ray Hobbs, is working as an outside sales rep for a local auto parts store. He becomes quite successful selling alternator and battery testers to his independent repair shop customers. He has to learn the technology to train the mechanics to use the testers and ends up starting his own independent repair shop.

Soon after that, electronics appeared in charging and ignition systems in the 1970s. Then, in the ’80s, computers appear on all GM passenger cars and a sure demise is forecast for independent repair shops. By the late ’80s, computers and fuel injection are the mainstays. Mechanics step up to the plate, learn a minimum amount of electronics, purchase scan tools and DVOMs and earn the more respectful title of technician.

Then came the 1990s, with serial data buses linking the increasing electronic content together. Again, a gloomy picture is painted for the small repair shop. Finally, the new millennium is here, along with more electronics needing to be programmed with factory scan tools and factory Web-accessed calibrations. The aftermarket service industry hangs in there and learns about J2534 reprogramming tools.

So here it’s 2008, and more than a million hybrid vehicles travel our highways, with some now over eight years old and in need of service. A dismal future once again is predicted by some for independent repair shops. Is it true that hybrid vehicles can injure or kill you, or at the very least intimidate you with the “techno-shock” of increased complexity? There are now mysterious new systems never before seen on an automobile and suddenly it’s like 1981 all over again. But, as happened in 1981, I believe independent shops will adjust and move forward.

The Perfect Storm

To be fair to the predictors of doom and gloom, we’re facing what might indeed be a so-called perfect storm of technoshock in the aftermarket repair industry. This perfect storm is a combination of mega electronics content, high-voltage systems and ultra expensive components. For example, a DC-to-AC inverter on a new Chevy Tahoe hybrid retails for $1440. A few wrong decisions in your service bay and you’re either dead, in the hospital or at the very least explaining why the repair order has $5000 worth of parts on it.

Exaggeration, you say? Did you know that there are over 50 electronic modules on a new Tahoe hybrid? There’s plenty of techno-shock on other models as well. Check out the expensive-looking hardware under the hood of the latemodel Lexus hybrid in the photo at the top left of page 74. Do you remember the last time you replaced an electronic component that wasn’t actually bad? We’ve all done it. We try to stay up-to-date and have the proper equipment, training and information, but it still happens. Sometimes it’s the equipment’s fault, other times it’s the manual’s fault. Even factory online manuals can lead us down the wrong path at times.

I was working on a new hybrid vehicle with a no-start condition recently. Guess what I did for three hours? Follow the factory manual until I was blue in the face. I finally got the answer from another tech who had more experience on that particular vehicle model. I’m glad I hadn’t started replacing parts yet. It was simply a high-voltage interlock circuit that had been pinched in an accident. I repaired the wire and the vehicle started. More often than not, the lack of a rocksolid foundation in basic electronics skills is the cause for replacing good parts unnecessarily. The way to avoid that perfect storm of repair disasters is good, old fashioned basic electronics training.

Strugglers Everywhere

I’m both amazed and proud of the wealth of knowledge possessed by many automotive repair technicians. I’m also equally amazed by how many technicians are lacking in basic electronics knowledge—the simple things like understanding series and parallel circuits and knowing exactly what this thing called continuity is.

I was teaching a class on serial data buses not long ago to a room full of ASE master techs. I thought we were running along pretty well, with everyone on the same page. I began discussing the two resistors wired in parallel between the two high-speed CAN bus wires used to aid in high-speed data transmission. These two 120-ohm resistors in parallel can be checked for resistance by measuring between pins 6 and 14 at the DLC (see Fig. 1). On some GM SUVs and pickups, one of those resistors is located in a module, the other in the wiring harness above the fuel tank. You can imagine what happens in a humid or salty environment. When one of those resistors doesn’t have a good connection, there can be problems with bus communications. No problem: Just throw an ohmmeter between those two pins and take a reading.

I asked the class what the ohmmeter should read. When only two techs knew the correct answer (60 ohms), I initially assumed they were just bogged down by the high-tech nature of the subject of multiplexing. So I moved to the other side of the whiteboard and drew a pair of turn signal bulbs in parallel—a good, down-to-earth comparison, I thought. Everyone knows what happens to resistance when you add more light bulbs (resistances) in parallel, right? Apparently not.

I came to the conclusion that a basic foundation in electronics eludes many of us who otherwise can do amazing things under the hood of a car. It’s not just techs who can struggle; those of us who teach techs can struggle, too. That revelation came more recently at an advanced hybrid training class. I was in a group of techs who were all ASE Master L1 certified. We were working on a late-model Honda Civic hybrid with a classroom-induced problem. None of us had fewer than 15 years of hands-on wrenching experience and all of us had become teachers for either colleges or factory training programs. We were following the factory manual when it prompted us to use a meter to check for continuity to ground on a particular circuit. One of the instructors connected his red ohmmeter lead to the circuit being tested and the black lead to chassis ground. The reading was 4.62 megohms (see photo below)—as in mega, for one million. Can you believe we had a split jury on whether there was continuity? Two master tech/instructors said, “Yes, there is continuity,” while the other two said “No, 4 megohms is not continuity.” Yipes!

Training Revival?

If you aren’t nodding your head and saying Amen! as you read this, you may be a candidate for some basic electronics training yourself. Forget about serial data buses for the moment. Forget about multitrace lab scopes. Get some basic electronics training right now!

There’s more information out there than time to learn it. Some information on electronics is essential, some just nice to know. While experts agree that the fundamentals are where we need to begin, the same experts often don’t all agree on the methods. I hear instructors, shop owners and seasoned techs differ on the matter of how to get today’s typical technician to understand electronics. Electron flow or conventional flow? Atomic theory (electrons, protons, neutrons, etc.) or maybe we should just compare current flow to something simpler? Then exactly what simpler analogy do we use? Water in a hose? Hydraulics in a pipe? BBs in a tube? There are many methods being practiced.

Which method is best? What’s the best way to learn a new language or master a musical instrument or mathematical concept? The one that works for you! The water, hydraulics and BBs analogies all make sense to me because I already have a grasp of electronics. You may want to try them all until you find one that clicks in your head.

Considering the rise in popularity of hybrids, we must know what conductors and insulators are, for safety’s sake; knowing the number of free electrons in a certain conductor is less than essential. The following topics are considered by most to be essential information in your quest for mastery of basic electronics.

Ohm’s Law. Ohm’s law is an essential item to master. Within Ohm’s law is the knowledge of how volts, amps and ohms interact within both series and parallel circuits (see Fig. 2). Remember those CAN serial bus resistors being just like turn lights in parallel? The more resistors you connect in parallel, the lower the total resistance. Put the resistors in series and now you’ve got a higher resistance value for the total circuit. This concept should become as instinctive as riding a bicycle if you plan to avoid that perfect storm of techno-shock that’s coming your way. When you have Ohm’s law firmly in your head, you’ll be surprised how much you use it.

Here’s an example of Ohm’s law in action from a recent Trouble Shooter column. The problem involved a pair of injectors (wired in parallel) that cut out as soon as the engine started up. The tech discovered that if he disconnected the alternator, the problem didn’t occur. When the alternator is charging, the voltage applied to the injectors (and everything else) is 14.5 volts instead of 12.5 volts. That means the current will be higher (amps equals volts divided by ohms).

A failing injector can have a little less resistance in its winding than it should—for example, 1 ohm instead of 2 ohms. The higher voltage can push the ECM’s current limit over the edge and cause the two injectors to shut down when this occurs. The slightly higher voltage with the alternator charging was not the cause of the injectors cutting out but rather what pushed the ECM over the edge trying to drive a partially shorted injector. That’s just one practical and profitable application of Ohm’s law.

Abbreviations. You must know your abbreviations and definitions. Continuity (remember those instructors and their 4-megohms argument?), open circuits, short circuits, partial shorts, etc., are all essentials to master. Capital M stands for million, lowercase m stands for milli, or one-thousandth, and k stands for kilo, or 1000. These are extremely important concepts. You’d be surprised how many of us don’t know these, or have forgotten. You don’t want to mess up on this if you’re measuring a contact at the end of one of those high-voltage orange cables on a hybrid. Be safe by wearing Class 0 insulating rubber gloves (see photo), and make sure your meter is on the proper setting for the potential voltage range.

Meter Knowledge. How well do you know your meter? Does it feature auto ranging or manual ranging? Does it have a fused or unfused ammeter? Does it have and can you use the Min/Max and Averaging feature? Can you use and properly interpret Hz and duty cycle? If you’ve got a hybrid in your bay, is your meter CAT III? Are the leads and alligator clips/probes CAT III-certified?

Circuit Testing. Do you know what open-circuit voltage is? For example, what should the voltage on the PCM’s switched ground side of a fuel injector be with the key on, engine off? If you said battery voltage, great! If you said zero volts, you’re incorrect but in good company. This simple concept confuses many techs. When you get it straight, you’ll find it a timesaver when trying to determine, with one single probe of your meter lead, if a relay or fuel injector winding has a power supply, good winding/coil and if it’s turned on or shorted.

Do you really know when to use an ohmmeter and when to use a voltage drop test? This is sometimes debated even among experts. Most agree that a voltage drop test is the best way to test a circuit for good connection/continuity. An ohmmeter puts out a tiny amount of current and does its own voltage drop test, so to speak. Sometimes that tiny amount of current is not enough to cause an intermittent connection problem to break down. Putting current through the circuit as is done in a voltage drop test often will cause the bad connection to act up, leading you to a proper diagnosis.

My personal belief is that a voltage drop test is preferred hands down over an ohms test, but I still use an ohmmeter to test for a complete circuit, as a backup. If the load device is nonoperational or simply switched off, there will, of course, be zero current flowing. This means there will be no voltage drop. The ideal circuit’s voltage drop is small—.5 volt or less per connection.

Unless you connect a power source, ground and your own load to the circuit you’re testing, a voltage drop test can be misleading. If you’re using an ohmmeter as a backup test like I do, remember, the ground of the vehicle carries current, too. Every electron that goes through those red or pink 12-volt wires returns to the battery on black wires or the metal chassis ground. The ground is never dead when current is flowing somewhere on the vehicle. The ohmmeter must be connected to a dead circuit. It will show erroneous readings if connected to a live circuit. Something as small as a dome light switched on can mislead you in an ohms test on a ground circuit. Disconnecting the battery cable before using an ohmmeter is the best practice. Learn to do these tests with 100% accuracy and you’ll be years ahead of many of your competitors.

Where do you stand on basic circuit testing? Do you understand how a voltage divider network works? It’s tough to fix steering wheel controls  without this knowledge. Most ABS wheel speed sensors and many engine control sensors also are involved with these voltage divider networks. In a nutshell, power (12 volts or 5 volts) is applied to one end of these series circuits and ground to the other. In the middle are two resistors. One resistor is a fixed value and is located in an electronic module connected to the circuit. The other is in series and varies with temperature or some other variable, or it could have a fixed value. The electronic module basically does a voltage drop test across its own fixed-value resistor to tell what voltage the other resistor is dropping. By doing this, the module knows things like what the engine coolant or air temperature is or if the knock sensor or ABS wheel speed sensor is disconnected.

Components. Do you know how basic electronic components work? Diodes, transistors, relays, resistors, capacitors, fuses, circuit breakers, fusible links and switches are everywhere. While you might never have to solder in a new transistor in your service bay, understanding what one does is important when you read a schematic. GM and Kia both use a transistor inside their ECMs to add or take away a pull-up resistor in series with the ECT. Taking this extra resistor out of the picture when the engine gets warm allows for better accuracy when measuring engine coolant temperature. Backprobe the ECT sensor when the ECM makes this change and you may mistakenly assume the ECM is bad (Fig. 3).

Sensors. Do you really know how sensors work? There are many types, including thermistors, potentiometers, Hall effect sensors, magnetic sensors, optical sensors, etc. Did you know that the two-wire ABS wheel speed sensor on some late-model GM vehicles produces a square wave? They’ve switched from two-wire magnetic sensors to a Hall effect style that doesn’t have a wire for a ground.

Are You Prepared to Weather the Storm?

Are you ready for future electronics subjects? Hybrid vehicles not only bring us high voltage but also three-phase AC. Terms like inductive  reactance and capacitive reactance are coming your way, along with such components as contactors, HV (high-voltage) interlock circuits, IGBT drivers, inverters, converters, ultra capacitors and brushless AC induction motors. Better catch up with the electronics that are out there now so you’ll be ready to understand newer electronics training associated with these eco-friendly technological wonders.

This article is meant to stress the need for basic foundational electronics know-how. If you’re not where you’d like to be in the field of automotive electronics, find out where you can go for training. Hands-on training works best for most of us in the trade. You can expect to pay more for hands-on courses, but you can also expect to learn and retain more. It’s very important to find a training provider/instructor who can speak to you on your level. Some techs thrive on lots of information thrown at them in a short time, while others say slow it down a bit. When you find a training provider/instructor who works for you, stick with him.

Whatever method you choose and wherever you go for electronics training, remember to start soon. Make it your goal for next year. If you achieve that goal you’ll be on your way to surviving the perfect storm of new vehicle electronics that surely is coming your way!

Originally printed by Motor Magazine September 2009. link

For 20 years Dave Hobbs has been a hotline adviser, field engineer and technical trainer for a major automotive parts supplier where he has assisted thousands of dealer and independent techs with diagnostic problems. An ASE Master L1 technician, sponsoring member of IATN, MACS and SAE, Dave spent over 15 years as an independent repair shop technician prior to joining the OEM world. Visit Dave’s website at www.hobbsautotech.com

Check out some of the training videos featuring Dave Hobbs at www.auto-video.com.