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The Spokesman-Review Newspaper The Spokesman-Review

Tuesday, March 26, 2019  Spokane, Washington  Est. May 19, 1883
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More than a mechanic

As I read of ever-evolving auto technology, including mechanical, electronic and computer advancements, I think of the individuals who diagnose, repair and service those systems. The simple term “mechanic” does not adequately label these people.

Today’s auto technicians, or “techs” for short, must learn and master myriad skills to effectively service our modern machines.  Basic understandings of fuel, spark, and timing are still needed, but knowledge of electronics, computers and software programming must now be added to the repertoire of today’s tech.

The best of them employ a blend of both traditional and contemporary skills.  They not only need to know traditional concepts like lubrication, bearing preload, fuel flow and electrical current, but they also must comprehend the complex computer systems that control the operation of newer motor vehicles.  Techs who grasp the “big picture” of all these systems and their interrelatedness are very skilled individuals.

As a driver, and as an owner occasionally needing auto service, it is important to realize what techs are up against when it comes to competent diagnostics and repair.

Auto-computerization really took off with the advent of electronic fuel injection, and has exploded since.  Because fuel injectors are activated with electronic signals, optimum mixture can be maintained via computer, influenced by input from a variety of electronic engine sensors.

The MAP sensor, or manifold absolute pressure sensor, is one of the major signal senders.  It can be described as an “electronic manifold vacuum gauge.”  The MAP sensor measures engine vacuum (load), and translates it to an electronic variable voltage signal that the computer can read and act upon.

The throttle position sensor (TPS) is a potentiometer, which, through resistance measurement, tells the computer exactly what position your accelerator pedal is in at any given moment.  It is mounted on the throttle plate rod, which is actuated by the foot-feed.

A mass airflow sensor also assists with fuel mixture by measuring the amount of air entering the throttle body orifice.  An oxygen sensor measures air coming out of the engine after combustion to check for unburned fuel, and tells the computer to make necessary fuel delivery adjustments.

Speed sensors inform computers of vehicle speed and wheel rotation, and play a role in the operation of anti-lock brakes, automatic transmission shifts, and all-wheel-drive.

Now automakers have even added radar, enabling features like adaptive cruise control, blind spot warning, lane departure warning and automatic braking.

New vehicles are complex, to put it mildly.  System failure diagnosis requires an astute technician who understands how to decipher scanned “trouble codes.”  When the computer receives an undesired sensor reading, it generally activates a “check engine,” “service soon,” or “maintenance required” light on your instrument panel.  Any technician can read these codes, but understanding them takes a pro.

For example, a dripping fuel injector will cause a rich mixture, and generate a trouble code indicating a bad oxygen sensor reading.  In this case, however, the oxygen sensor is not the problem.  Other times, a bad sensor, such as a MAP sensor, may cause a bad reading for an oxygen sensor.  Scanning for trouble codes will show both sensor faults, and it is up to the technician to determine which one is actually inoperable.

Please consider and respect the expertise required of automotive technicians — the vehicles they now service demand wisdom derived of past and present knowhow.

Readers may contact Bill Love via e-mail at