Mark Giammalvo specializes in driveability diagnostics at his family business, Sam Giammalvo's Auto Sales & Service, Inc. in New Bedford, MA.
Mark, who has been with the business for
over 20 years, is an ASE
Master Technician and Parts Specialist. He also holds the ASE
L1 certification, and has an associates degree
in business management.
(Printed in the Journal
of The Alliance of Automotive Service Providers, AASP)
Recently, I've had the opportunity to answer a lot of technicial automotive industry questions. Julia Scheeres, from wired.com, has been asking me for automotive technical information she can use for her internet articles about modern day automotive complexities.
Below is a copy of our recent email discussion:
Julia Scheeres wrote:
Hey Mark - thanks a lot for your help on the code story. I'm doing a follow-up article on computer malfunctions in cars. I've heard from people who attributed electronic misfirings to steering wheel lock up, sudden acceleration and stalling at freeway speeds. Do you have any choice anecdotes from your customers along these lines?
Subject: Re: follow-up
Date: Thu, 03 Jun 2004 14:10:09 -0400
From: Mark Giammalvo <firstname.lastname@example.org>
To: Julia Scheeres <email@example.com>
Hi Julia. Good to hear from you again.
The average automobile owner has no idea how many electronic items are in the
average car. Worse yet, the motoring public does not realize how many of these
items can render a car inoperative without warning.
I have spent 15 of the last 21 years performing automotive diagnostics and repairs and what I have seen is both frustrating and scary. Just about all vehicles manufactured since 1980 have an engine management computer. From 1985-1992 most have an engine computer, transmission computer and body computer. Cars newer than 1992 now have those 3 computers plus extra computers for air bags, anti-lock brakes, traction control, steering control, throttle control and more. Most cars don't even have a speedometer cable anymore. That is interesting when you think about it. The auto manufacturers could build all the cars with a digital dash but they don't. Most cars still have a speedometer needle. How is this so? The manufacturers have gone through the trouble to take the speed reading off a speed sensor in the transmission, run that signal to a computer that runs an electronic motor that spins the speedometer needle. In a sense, the owner thinks the car is still sort of simple and reliable because they still see the old speedo needle. They still think its and old fashioned cable connected to the transmission and spinning with the wheels. Little do they know the amount of electronics in the dash present to they can still "feel" that their car is simple, and reliable. It is amazing. Its as if the corporate auto people don't want the consumers to know how technical the cars have become. Perhaps its intentional.
Julia, some times I catch myself thinking of these auto complexities when I am driving on my vacation trips. As I am driving, I find myself drifting off thinking of what is going on under the hood: Fuel and air are entering the engine cylinders and the ignition system is firing the spark plugs at the precise time to cause an explosion to push down a piston that turns a bunch of gears in a transmission that in turn spins an axle that turns the wheel and makes the car go foreword. During all this action the mass air flow sensor is telling the engine computer how much air is entering the engine. The oxygen sensors are telling the computer how rich or lean the exhaust system is. The crankshaft and camshaft position sensors are telling the computer exact cylinder position about 2,000 times per minute. The coolant temperature sensor is telling the computer how hot or cold the engine is in order to run cooling fans and control fuel delivery and air conditioning load. The intake air temp sensor is telling the computer exact air temperature for fuel delivery calculations and your dashboard outside temperature display reading. The computer is acting on a program to command outputs like the fuel injectors and fuel pump which are doing their thing thousands of times per second. I think to myself: "My God, if any one of these sensors quits (and they can at any time) this car is dead in the water!" You might say I know too much. Sad, but true.
Not to mention that many cars do not have a cable connection from the gas pedal to the engine. A lot of cars are "drive by wire" now in that the gas pedal has a position sensor. The position sensor tells a computer to quickly move a lever on the throttle of the engine. These electronic components are so fast that you "presume" you are controlling the throttle with a cable. There is no delay from stepping on the pedal to the engine responding.
Whew! Hope that info helps.
p.s. You might be also be interested in an article I did recently here...