A Basic Guide to the Computer in Your Car

Computer Operating Guide  in Your Car

Did you know that modern cars can have over 80 different computers scattered around the car? These control everything from your automatic windows to your stereo to the brake system to your engine. The computers are all hidden behind body panels, in the engine compartment, and dozens of other places. In fact, the only sign of computers most drivers will ever see is the console interface.

Emissions Standards:  The Birth of Car Microprocessors

Car computers really got their start with the introduction of the catalytic convertor and electronic fuel injector. Before these systems, the fuel/air ratio was controlled by the carburetor, which could be more than a little imprecise. A catalytic convertor requires a precise fuel/air ratio (1:14.7) in order to be effective in eliminating emissions. As emission standards got more and more strict, more control was needed.

Enter the first car microprocessors. The chips were nowhere near as powerful as the ones in personal computer, but they didn’t have to be. After all, they have to process a lot less data and programs. These chips made it possible for the fuel/air mixture to be constantly monitored and adjusted to make sure it had the right ratio. As technology got more advanced, the uses for auto computers multiplied.

The CAN

As more and more computers were added to cars, something had to be added to tie them all together. This is where the Controller Area Network, or CAN, comes in. The CAN creates a complex network that connects all of the computers throughout the car. The modern CAN design doesn’t even have a central hub or router. All of the individual Electronic Control Units (ECUs) are linked to the network, allowing them to interact seamlessly.

Parts of an ECU

That network would be nothing without the ECUs. These are the actual workhorses of your car’s computer system. On the outside they tend to look like boxes, but inside the housing is a circuitboard with several different components, including:

Analog-Digital Converters:

Many of the sensors throughout the car are analog, but the chip can only deal with digital data. The converters turn those analog signals into 1’s and 0’s so the chip can use them.

High-Level Digital Outputs:

That digital signal hits the processor, which runs it through programming. Depending on how the programming reacts, the chip will send signals through the outputs to operate things like fuel injector, spark plugs, and more.

Digital to Analog Converters:

Like the sensors, most of the parts in a car are mechanical, meaning they need analog signals to run. The convertors take the digital signal and make it into the voltage that’s needed to power the mechanical parts.

Signal Conditioners:

Sometimes that voltage needs to be adjusted to work with certain parts. These conditioners are circuits that make any necessary voltage changes, and are the last link in the ECU chain.

Diagnostic Ports

There are various ports built into the ECUs and the CAN that allow access to the system. Mechanics will use these to connect diagnostic computers to aid them in finding problems with the engine. They also make it easy to switch out faulty ECUs or parts of the CAN without a lot of network splicing.

But they have another common use. Mechanics and car owners can use these diagnostic ports to connect to the engine control module. That connection can then be used to remap the computer, add performance chips, or tune the software.