by Jim Kerr
I was looking through a 1930’s Ford shop manual last week. The car’s wiring diagram was printed on a single page. After all, there were only the lights, horn, generator, starter and a couple gauges to connect. Today, a vehicle’s wiring harness has thousands of connections and kilometres of wire. There are accessories and features that are only limited by your imagination. I even told a new Cadillac I was testing the other day to roll up the windows. That’s right. I told it to do it – no window buttons to press, just say the right commands.
Voice command systems are available on other vehicles too. Jaguar, BMW, Chevrolet, and many others have optional systems that can be accessed with voice commands. At first these systems may sound frivolous but soon they become natural to use and keep the driver’s eyes on the road, especially in rush hour traffic where a split second can be the difference between a fender bender or not. What do voice command and other high tech options have in common? Communications. Today’s cars and trucks are being controlled through computer networks where communications are key.
There are many different types of vehicle communication systems. Fortunately, many of the communications are based on industry-wide standards established by the Society of Automotive Engineers (SAE). If not for these standards, the market place would be chaos. Even with standards in place, there are many types of communications protocols. Some vehicles use only one type. Some use two and there are many that use three or more on a single vehicle.
When computer controlled fuel injection first entered the market, data communications was not a priority. All the inputs and outputs were hardwired to the computer. Some manufacturers used scan tools (hand held diagnostic computers) to communicate with the vehicle computer but the data was limited. Most cars were diagnosed using symptom charts.
In the 1980’s, emissions legislation created the push for communications to enable diagnosis. By 1996, a new communications standard evolved because of increased emission regulations. With a baud rate of 10,400, much faster than the previous data communications rate, diagnosis of fuel injection, antilock brake and transmission computers was more accurate and quicker.
Now, technicians are seeing another communications standard evolve into our vehicles. I say evolve, because many vehicles use combinations of older and new communications systems as a transition. The standards for this new system separate vehicle electronic systems into priority groups. Engine/transmission controls and safety systems such as ABS, stability control and air bags communicate at 500,000 baud. This is nearly 50 times faster than the old systems. Convenience systems such as power windows, navigation, audio systems and climate control operate at 125,000 baud or 33,000 baud. Even the slowest data rate is 3 times what it was in the past.
Every manufacturer seems to have their own name for the latest standard to add to the confusion but they are very similar systems in operation. Chrysler calls theirs a CCD buss, Ford refers to their system as Multiplexing and GM describes their network as GMLAN. All of these systems are a communications network that ties many modules and computers together on the vehicle.
This time, the push for the new communications standard seems to be consumer demand. Start looking at new cars and you find memory seats, keyless entry systems, theft alarms, high end audio systems and DVD entertainment systems offered on many vehicles. Navigation systems, Bluetooth connections for cell phones, heated seats, stability control, voice command – the list seems endless. High speed communications are what make many of these systems both possible and affordable. I am not sure if the consumer is demanding these features or if the manufacturer is offering them because they want to lure new buyers, but whether we want it or not, vehicles have more features than ever before.
How does this impact vehicle owners? Vehicles are safer. Communications link ABS, stability control, crash avoidance and emergency response notification together and react as a system. Vehicles use less fuel, produce fewer emissions and are more fun to drive because integration of engine, transmission, climate control and suspension communications systems.
Vehicles are also easier to diagnose when there is a problem. High speed communications enables technicians to operate systems quickly and isolate faults more accurately. The communications systems are complex to understood but shorten diagnostic times.
There are disadvantages. Radios are integral to the operation of many systems. You can’t change to another easily. Leave a key in the ignition and modules may “stay awake”, draining a battery in a few hours or less. Overall, the advantages seem to outweigh the disadvantages.
In the future, even economy cars will have features that today’s high end vehicles offer. Communications are what make it possible.