Just a single decade ago, many industry experts speculated that 80% of the workflow passing through an independent repair shop would involve some type of high-level diagnostic process. Today, it’s obvious that, with the infusion of electronic operating systems, high-level diagnostics is now approaching that level of total workflow. Nevertheless, many others continue to ridicule the idea because everybody “knows,” for example, when a PCM is shot, or when the overdrive in an automatic transmission is slipping, or when a spark plug wire goes open-circuit. Who needs a diagnostic procedure to know that stuff?

In today’s technical climate, many of these same shop owners are now facing a “Diagnostic Dilemma” of their own. Their technicians may be having an increasingly difficult time diagnosing “simple” failures, such as engines that won’t crank, interior lights that won’t go out and warning chimes that mysteriously sound off going down the highway. As one might suspect, many shop owners haven’t come to grips with the fact that a powertrain control module (PCM), body control module (BCM) or a dedicated control module now controls cranking operations, convenience items and safety equipment. To make the situation even more challenging, multiplexed electrical systems are now using inputs from a variety of powertrain and chassis sensors to control simple functions as when the rear hatch lock disengages on a modern SUV. Isn’t anything made simple anymore? Not hardly.

To make the diagnostic skill issue even more contentious, the industry at large has never taken the diagnostic process seriously. Dealership shops are well known for allotting diagnostic time in mere tenths of an hour. Many dealerships also subscribe to the “line mechanic” system in which work is assigned to vacant stalls, not to technicians with the appropriate diagnostic skill levels.

Unfortunately, this philosophy carries over to the independent sector as well. Too many shops still don’t charge for diagnostic time nor do they reward those technicians who devote a disproportionate amount of their time, energy and financial resources to acquiring high-level diagnostic skills. The end result is the developing crisis in which we have many technicians for whom the diagnostic process exists only as hindsight.

Assessing Diagnostic Skills
Having taught adult auto mechanics for a number of years, I don’t think there is a perfectly accurate way of measuring or defining a technician’s diagnostic skills. Interestingly enough, a few educational theories describe how a person’s heredity and early environment determines his ability to deal with abstract issues. While it’s very easy for most technicians to understand how the camshaft opens a valve, it can also be equally as difficult for some to understand how a silicon chip rearranges its molecules in order to control fuel injector pulse width and calculate fuel trim numbers.

The A, B, C Techs
For the purposes of illustration, let’s assume that a top-drawer or “A-level” technician is typically an ASE Certified Master Auto Technician (CMAT) with the L-1 advanced engine performance certification. The L-1 certification, as you may recall, is devoted to engine electronics diagnostics. The A tech who has earned the L-1 certification is usually one who thrives on the diagnostic process. And, because he has excellent logic and critical thinking skills, he also may be inquisitive, academically oriented, self-educated and possibly college-educated to boot.

The “L-1” tech may also be the one attending the most training classes, reading the most trade magazines, and the most likely to dial up iATN’s Technical Discussion Forum every night in order to see what’s happening in the world of rocket-science diagnostics. As a result, the A tech usually has a good systems knowledge of most vehicles and has usually developed a set of “customized” diagnostic strategies that he uses to cut to the heart of the everyday diagnostic problems that he encounters.

Again, for purposes of illustration, let’s say that a “B-level” technician has the CMAT certification, but not the L-1 certification. The B tech might be the guy who cranks out 60 flat-rate hours in a 40-hour workweek. He’s good at diagnosing mechanical failures, but he’s uncomfortable grabbing a scan tool and a lab scope to diagnose an intermittent electronic glitch. The B tech may have a good grasp of basics, but not have a great deal of systems knowledge. Not that the B tech can’t advance to the L-1 level, it’s just that he may be too busy doing general repair work. And then, sometimes the B tech just plain doesn’t like doing electronic detective work!

Last, let’s look at how the C tech fits into the diagnostic formula. The C tech might be a young tech who has earned several of the eight basic ASE auto technician certifications or he might be an older tech who has let technology pass him by. The C tech might be a skilled alignment and brake tech, or he might be the engine rebuild specialist. But, an electronics diagnostic tech, he’s not.

Does his lack of electronics diagnostic skills mean he should be replaced with an A or B tech? Of course not! Most of the work done in the automotive service industry is done by the C tech and, like the A and B techs, the C tech has his place in the diagnostic scheme of things.

Although the above classifications certainly aren’t meant to stereotype technicians, they do illustrate the differences that might exist among a group of highly qualified technicians. With that point in mind, let’s go through my most recent case study book in order to illustrate what level of diagnostic ability might be required in each of the following scenarios.

B+ Amnesia
The first case study that comes to mind is a 1998 Jeep Grand Cherokee that, according to the owner, misses fourth gear when the automatic transmission is cold and stalls when the engine is hot, and that loses the clock portion of the console display when the engine is started. At first glance, this definitely looked like an A-tech problem but, upon opening the hood, I noticed that the corrosion on the battery terminals looked like a high school science experiment. After connecting my scan tool, no trouble codes were detected, but I did notice that the scan tool would lose its memory when I cranked the engine.

To confirm my suspicions about the battery, I connected my DVOM to the battery in the min/max recording mode. When I cranked the engine, the battery terminal voltage dived to 5.5 volts. Further testing with a load tester and an electronic battery tester concluded that the battery was in poor condition.

As suspected, although the permanent magnet, reduction-gear starter cranked the engine at normal speed, the system voltage dropped well below the 8 or 9 volts required to fully power the PCM. As the engine cranked, the loss of voltage erased the PCM’s adaptive fuel memory and any diagnostic codes that might have been stored in the diagnostic memory. A battery replacement solved the driveability and the console display problem.

So, is this an A, B or C tech level problem? Given the way I approached the issue, it was an A tech level problem. But either a B or C tech could have solved the problem if the shop’s standard operating procedure was to test the battery of every vehicle that comes in the door. Of course, I had a Jeep in a few days before with a similar problem so, instead of testing the battery, I merely confirmed that the bad battery was affecting the PCM’s adaptive memory. Could a B or C tech have solved the problem? Certainly, if they had followed the shop’s battery testing policy!

Stinky Business
Let’s jump over to an ASE-style “Mechanic A/Mechanic B” problem. A 1993 Ford E-150 van with a 5.8L engine and automatic transmission came into the shop for a second opinion about a rotten egg smell coming from the exhaust. Another shop claimed the smell was caused by a faulty catalytic converter. I felt, on the other hand, that an over-rich air/fuel mixture caused by a stuck fuel pressure regulator or an out-of-calibration MAP sensor was creating the smell.

Again, the battery looked like a chemistry experiment, but tested good. Before disconnecting the battery terminals for cleaning, however, I retrieved a continuous DTC 128, which indicated that the MAP sensor had operated out of range. A continuous DTC 173 also indicated that the engine was running rich.

Okay, could a B or C tech have diagnosed the problem? Since Ford’s H1 diagnostic tree lists a MAP sensor as a possible cause, it would be very easy for a C tech to assume that a faulty MAP sensor caused the problem. Sure, the MAP code indicated an intermittent out-of-range condition, but testing the MAP showed 138 Hz KOEO, which is correct for our 8,000′ altitude. An A tech, on the other hand, would remember that the MAP DTC is stored only when the intake manifold vacuum reading doesn’t agree with the throttle sensor position and engine speed.

So that leaves us with the DTC 173, which is caused by a rich air/fuel mixture keeping the O2 sensor pegged at 0.9 volts. Although not indicated in the Ford H1 chart, the next logical step is to see if the fuel pressure is in its normal range of 35 to 40 psi. The test itself revealed about 90 psi at the fuel rail, which explained why the engine was running rich and why the exhaust smelled like rotten eggs.

I would say that this is an A tech problem because first, the tech had to know that the rotten egg smell indicated that the catalytic converter was trying to oxidize excess fuel. Second, the tech had to know that the DTC 128 indicated that the intake manifold vacuum was low, not because of a bad MAP sensor, but because the engine was being drowned in fuel. Third, the tech had to know that stuck fuel pressure regulators are a pattern failure on EEC-IV Fords. In fact, this was my second stuck Ford pressure regulator in two days.

“Popping Codes”
Let’s continue with a 1993 Ford Escort that intermittently illuminates the Check Engine light going uphill and jerks at closed throttle going downhill. The Escort was unusual because it had only 40,000 miles on the odometer. The troubles codes were as follows: DTC 171-system adaptive fuel lean limit reached, DTC 172-system indicates lean (no O2 sensor switching), DTC 181-system adaptive rich fuel limit reached, DTC 186-injector pulse width longer than expected (rich), DTC 338-engine coolant sensor voltage too low for operating conditions. The data stream information, strangely enough, appeared normal.

Now, let’s turn this job over to the C tech. C tech has read enough about scan tool diagnostics to know a trouble code when he sees one. After all, this baby is really “popping” some codes, agreed? So C tech might begin by replacing the oxygen sensor to remedy DTCs 171, 172 and 181. He might also toss a new thermostat to remedy DTC 338, which indicates an engine coolant temperature problem. Close, but no cigar because C tech is ignoring the basic relationship of the trouble codes. He’s forgetting that, with the exception of DTC 338, the first four DTCs are all fuel trim-related problems and they’re bouncing from rich to lean because the PCM can’t establish good fuel control.

Now, for the rest of the story: since I noticed that the engine hesitated slightly during a throttle snap, I decided to attach a lab scope to the “D” terminal on the mass airflow (MAF) sensor. As I opened the throttle, the MAF voltage rose and then dipped abnormally, which indicated a possible Ford pattern failure. Evidently, when the air filter was replaced, a large, piece of dense, black fuzz stuck to the mass air flow sensor resistors. A light cleaning removed the fuzz from the MAF resistors and remedied the hesitation problem. As for the DTC 338 or coolant temperature code, I’ll leave that for later, since the coolant level and cylinder head temperature tested good.

I believe that the above is an A tech problem because the tech must have a systems knowledge and must know how to draw conclusions related to a series of trouble codes, a lab scope waveform and a scan tool data stream.

Last, let’s look at how an A, B or C tech might deal with a 1997 Dodge Intrepid with an intermittent Malfunction Indicator Light (MIL) that developed shortly after the owner had a timing belt replaced. Actually, it doesn’t take a rocket scientist to realize that one of the 3.5L engine’s camshafts might be out of time. If C tech would look at a firing order schematic, he could easily see that DTC P0301, 303 and 305 (misfire on cylinders number 1, 3 and 5) were originating from the right-hand cylinder bank. Retarding the right-hand camshaft one tooth remedied the problem. As for A or B tech, diagnosing those multiple misfire DTCs are usually duck soup!

Diagnostic Helpers
How do we make a B tech out of a C tech? The answer is easy: teach him to use the tools at hand. Several major scan tools, for example, contain pattern failure data bases that are designed to help any A, B or C tech deal with an unfamiliar problem or operating system. In addition, tech hotlines are available that list pattern failures and their solutions either on paper or online.

Next, each shop should put together a set of basic diagnostic procedures. Before work begins, a fluid level check should be mandatory because, in the example of the Ford Escort, a low coolant level could cause the DTC 338. Next, any electronics diagnostic procedure should begin with a battery test. Any system should also be tested for diagnostic trouble codes. Some very inexpensive “code pullers” are available that can give the C tech that capability without tying up an expensive scan tool. Last, many problems can be solved by inspecting the vehicle’s physical condition. Attaching or tightening loose vacuum lines and/or loose MAF sensor intake ducts, and inspecting ground connections may eliminate many seemingly “complicated problems without ever having to consult a diagnostic chart or attach a single piece of test equipment.

Subjective Judgments
Given that approximately 1,700 different vehicle models are coming into the domestic market each year, it’s no wonder that the automotive service industry is being driven into skill specialization. Whereas only about 4,000 pages of technical information confronted a master technician when I started 40 years ago, almost 2 million pages of information in the current market now confront a CMAT-L-1, not to mention the CMAT B tech or the ASE-certified C tech. It’s mind-boggling, to say the least, and it’s in no small part responsible for today’s “Diagnostic Dilemma.”