A favorite pastime of mine is to hang out at the coffee pot end of the wholesale service counter and observe the comings and goings of my jobber store’s retail clientele. One minute it’s the high school kid attempting his first oil change; the next it’s the hesitant housewife picking up some replacement parts for her husband’s weekend automotive project.

Some retail customers have researched their problems on the Internet and come away either remarkably well-informed or completely confused. Another DIYer is depending upon a tip from an equally misinformed “mechanic friend.” In these cases, the DIYer might feel it’s the parts professional who is confused, not him.
Because of misinformation, most DIYers simply underestimate the time, training and tooling that is required to repair vehicles manufactured since the 2004 model year, when most conventional vehicle functions became electronically controlled. At best, the average DIYer is certainly in over his head due to the lack of professional-level tooling, technical expertise, repair information and experience.

Unfortunately for parts professionals, the lack of technical know-how on the part of the DIY customer often results in poor customer relations and excessive warranty returns. But it takes all types of retail customers to help reach each day’s sales goals. Some can benefit from help; others are completely in over their heads. To help each DIYer customer fix his problem or tell him when to quit, let’s explode some old myths and explore some modern technology.

A TECHNOLOGY OVERVIEW
Since 2004, auto manufacturers have changed from simple fuel-injected engines operated by a single engine management computer to what is known in the industry as the Controller Area Network (CAN) communications protocol. The purpose of CAN lets various computers and modules share information and make extremely fast and complex math calculations. If, for example, the vehicle becomes involved in a serious collision, CAN keeps the vehicle occupants safe by allowing the anti-lock braking, vehicle stability control, cruise control, electronic throttle, air bags and power door lock systems to make split-second decisions in a highly prioritized and coordinated manner.

CAN technology is rapidly leaving many technicians behind because most vehicle operating systems are now integrated with each other. For example, starters on many vehicles are now actually operated by the engine’s Powertrain Control Module (PCM). In contrast to conventional starting systems, vehicle owners often notice a slight lapse between the time the ignition switch was turned to the “start” position and the time the starter actually engaged. The difference is that, instead of directly activating the starter, the ignition switch is simply commanding the PCM to “start” the engine.

And, if indeed a person is knowledgeable, it’s impossible for any professional to explain it in “20 words or less” to somebody who’s technically illiterate. For example, a single failed module in a networked system can cause a general system failure by breaking the communications links among the remaining modules. This type of problem is tough for even the best professional technician to diagnose, let alone the untrained guy working in his backyard. Consequently, the best any of us can do is to understand that even the most common diagnostic repairs are now made very complicated by modern CAN communications technology.

GETTING THE FEELING
I don’t think it takes a Freudian psychologist to understand when the average DIYer is in over his head. An obvious unfamiliarity with parts terminology is an early warning sign.

Of course, cataloging errors and inconsistent terminology compounds terminology problems, even at a professional level. But, when a DIYer places a used part on the counter and doesn’t understand its name or function, you’re definitely looking at a person operating at his limits of technical competency.

Another indication of the DIYer being in over his head is when he/she begins asking for technical advice or information. Because many parts professionals are ASE-certified parts specialists, many have a working knowledge of the parts they sell. But, even if the parts professional is an ASE-certified Master Automobile Technician (CMAT), he or she will have trouble deciphering exactly what the DIYer’s problem might be or exactly how to address it based on the DIYer’s description of the problem.

Last, the amount of information required to diagnose and repair a modern vehicle is mind-boggling, with the volume of technical information being such that it’s now delivered to independent shops online. The small paper-back repair manuals sold at your front counter cover only the most general repair and maintenance operations. For this reason, any DIYer armed only with a paperback manual can be well in over his head if he attempts a complex repair.

MODERN TOOLING
Most modern vehicle technology requires at least two years of formal education and at least several years of in-field work to develop enough familiarity needed to diagnose and repair various basic operating systems. Most engine control and powertrain management diagnostic procedures require far more than diagnostic trouble code (DTC) retrieval capability. Current diagnostic procedures require also bi-directional control of various components like cooling fans, fuel pumps, EGR valves, exterior lighting, windshield wiper, horns and even anti-locking braking systems. So, solving technical problems for customers can prove to be much more complicated than simply providing a few technical tips in “20 words or less.” To help keep our DIYer out of trouble, let’s look at a few common examples of how automotive architecture has changed in recent years.

ALTERNATORS
The old 1960s-era method of testing an alternator by removing a battery terminal while the engine is running should be absolutely discouraged because the battery protects modern electronics by acting as a capacitor (or an electrical sponge, so to speak) to absorb transient voltage spikes generated by ignition systems, switches and solenoids. When the battery is taken out of circuit with the engine running, the on-board electronics are left with no protection against voltage spikes or excessive charging voltage. In extreme cases, the resulting damage can amount to a five-figure number.

Another obsolete test alternator procedure is to look for a charging voltage of about 14.2 volts at 70 degrees F. On modern vehicles, the PCM controls the alternator charging rate according to electrical load and driving conditions. In some cases, the alternator will be charging at a very low voltage because the battery is fully charged and system demand is low. The only valid test on vehicles with load-sensitive charging systems is to attach a scan tool that will command the charging system to perform a self-test. The other alternative, of course, is to remove the alternator for bench-testing.

BATTERIES
Because very little battery amperage is required to crank a modern gasoline engine equipped with electronic fuel injection and ignition, the primary role of the battery has changed. Today’s battery now acts as an electrical capacitor to maintain a constant voltage in the on-board electronics and to maintain a reserve electrical supply to keep the on-board electronics powered when the vehicle is parked.

To achieve these goals, the battery’s Cold Cranking Amperage (CCA) must match the original equipment specifications. Batteries with insufficient CCA will not maintain terminal voltage at the engine computer during cold-weather cranking, which can cause intermittent starting and cold-driveability complaints once the engine is started.

TRAILER LIGHTING
Recently, I diagnosed a 2003 Dodge truck on which a technician had attempted to solve a malfunctioning right-hand trailer turn signal by installing an aftermarket signal converter on that circuit. Although the technicalities of what he was attempting are too complex to explain in this space, suffice it to say that modern exterior lighting systems don’t take kindly to backyard modifications.

This Dodge incorporates an Integrated Power Module (IPM) with the conventional underhood fuse box. The IPM contains a “Front Module” that controls, among other things, exterior lighting and the trailer turn signal relays. Unfortunately, the right and left turn signal relays can’t be independently replaced in this module. So the repair required a rather expensive replacement of the Integrated Power Module assembly. Even when today’s DIYer approaches something as simple as a bad trailer light circuit, he’ll probably find that modern technology has rendered all of his old “shade-tree mechanic” techniques useless.