The car’s instrument cluster is just one example of how automotive electrical design and communication standards have made designing and constructing cars a little easier.

The instrument cluster collects and displays data from different parts of the vehicle. Most of this data has been previously used by other modules in the car. For instance, the ECU knows the temperature of the coolant, the transmission controller detects the vehicle speed, and the controller for the anti-lock braking system (ABS) knows when there’s a problem with the brakes.

All the different modules send this information onto the communications bus and, several times a second, the ECU sends out information containing a header and the data. The header is simply a number that identifies the data as either a speed or temperature reading while the data is the actual speed or temperature. Another module on the instrument panel also looks for certain packets — whenever it receives one, it updates the correct gauge with the new value.

Most car manufacturers purchase their instrument clusters fully assembled from a supplier, who designs them according to the carmaker’s specifications. For both the carmaker and the instrument cluster supplies, this designing the instrument panel far more easier.

Instead of carmakers telling their supplier how each gauge will be driven, the carmaker can just provide a list of the packets of data. Then, it is the carmaker’s job to ensure the right data is routed to the communications bus. It is also easier for the supplier because the details of how the speed signal is generated, or where it’s coming from, are not necessary to the design process. Instead, the instrument panel just observes the communications bus and updates any gauges when new data is received.

With communication standards like this, it is simple for car manufacturers to outsource designing as well as manufacturing: the carmaker isn’t bothered with the details of how each gauge or light is created and the supplier who creates isn’t burdened with figuring out where the signals are coming from.

More information on automotive diagnostics:

• Smart Sensors in Late Model Cars
• ECU Components in Automobiles
• Automotive Diagnostics
• Engine Knocking
• Engine Efficiency
• Engine Diagnostic Service
• Check Engine Light
• Smog Check

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