Each year, cars seem to get more and more complicated. Today’s vehicles have as many as 50 microprocessors under the control of a central computer. From sophisticated engine controls to high-end electronic systems, it takes sophisticated training and specialized equipment to service and maintain your ride.
Before emissions laws were enacted, cars and trucks ran quite nicely without the aid of microprocessors. However, increasingly stricter emissions standards required sensors, controls and computers to regulate the air/fuel mixture so the chemical makeup of the gases reaching the catalytic converter could be neutralized as the engineers had intended. Today, the descendents of these pioneering processors are in charge of every aspect of the internal combustion and exhaust treatment processes. As your dealer, it is our job to confirm these complex systems are working properly, discover when they aren’t and fix them properly. The days of the conventional “tune-up” are long gone!
Controlling the engine functions is the most processor-intensive job on your car, and the engine control unit (ECU) is the most powerful computer on most cars. The ECU uses what we call a closed-loop control scheme that monitors and controls inputs and outputs of a system, managing the emissions and fuel economy of the engine, as well as a host of other functions. Gathering data from dozens of different sensors, the ECU knows everything from the coolant temperature to the amount of oxygen in the exhaust. With this data, it performs millions of calculations each second, including looking up values in tables, calculating the results of long equations to decide on the best spark timing and determining how long a fuel injector is open. The ECU does all of this to ensure the lowest emissions and best mileage.
The ECU with its team of processors consists of sensors with analog-to-digital converters needed to facilitate ECU control. When the ECU must order a component to make an adjustment, it does so with a digital-to-analog converter to transform the digital sequence into an analog voltage. Then there is the CAN standard (controller-area-networking) that allows all the components to communicate with each other. All this interaction goes on at speeds approaching those in your home computer.
So how do we know what’s going on in there when you bring your vehicle in for service? Well, we tap into the “communication bus,” the method by which each component, module and sensor communicates its status to a central memory module that stores the information, compiling both the nominal (good) and the faults (bad). There is a multi-pin information port in each vehicle where we plug in our computers. We download this information to our diagnostic equipment in the service department.
Our technicians use the information to verify proper function and diagnose problems, especially intermittent problems that are notorious for disappearing as soon as you drive into our service department. The information is also useful for anticipating and heading off something that could turn into a major repair. This is why cars still have service intervals recommended by the manufacturer. As they say, an ounce of prevention is worth a pound of cure.
This ECU resets and re-tests all sensors and indicators each time you start your vehicle. Some car systems are capable of correcting some minor abnormalities. That’s why you may see a warning light on your dashboard once and not see it again. However, if the light continues to come on after multiple car starts, it is probably sensing something it can’t correct. When the dreaded “check engine” light comes on, you know the ECU has detected problems that it wants fixed. It’s our job to find out what is wrong and fix it.
As any “shade-tree mechanic” will tell you, today’s cars and trucks are too complicated. We agree they are complicated, but having the right diagnostic systems and tools makes all the difference.
In fact, much of the car’s mechanical systems have not changed all that much. Twenty or more years ago, if the throttle linkage had a problem, you opened the hood and wiggled the rod that moved the throttle blades. If it didn’t move at all, it was stuck. If it moved poorly, it was just sticky. If one end moved and the other end didn’t, something was broken. However, most cars today are throttle-by-wire. The computer sends electrical signals to an actuator and that device moves the throttle blades. Your foot moves a pedal with a variable resistor attached to it to send data to the computer. It’s a layer of complexity removed from the mechanical linkage.
Today, we figure out the problem using systems analysis with the help of our specialized computers. Once we understand the problem, fixing your vehicle is still based on the basic principles of mechanical, electrical and hydraulic systems.
Bottom line? If it’s broke, we can fix it!