Years ago, a technician might spend five minutes diagnosing a car and five hours making the repair. Today, we might spend five hours running tests and diagnosing the vehicle, and five minutes repairing or putting a component on it. The use of electronics drives this change.

Vehicles today have a tremendous number of electronic systems. It is not unusual to find between five and fifteen computers on any given car. It is imperative that all those computers communicate with each other. The main computer is the Powertrain Control Module. All other computers must communicate with this “mission control center” through a CAN—Controller Area Network. Investigating these various computer systems can become complex.

A modern vehicle has far more computing power than the Apollo spacecraft that landed men on the moon. Press on the gas pedal and make the car go faster? How does that happen? Years ago it happened with a mechanical link from the gas pedal to the carburetor. Now it’s simply activating a switch that changes electrical resistance telling the onboard computer system you want to go faster. The computer then controls the amount of fuel flowing into the engine.

Press the brake pedal and a switch sends power to the brake lights, right? Not anymore! Now the brake switch tells the computer you are braking and the body control module (BCM) sends a signal to the brake lights and to the onboard computer telling it you are braking.

Does this sound more complex than it needs to be? Maybe, but these are the things that allow us to enjoy fuel economy no one thought possible twenty years ago. Diagnosing these systems is where experienced, certified technicians are worth their weight in gold which brings us to the answer of the headline.

Testing and diagnosis of these systems requires very expensive testing and monitoring equipment and specially trained technicians with a high degree of sophistication and experience. The days of “looking” at a car and knowing what the problem is is far in the past. The knowledge and equipment needed to test even simple sounding issues requires that the time, equipment, and training necessary must be paid for in order to keep the shop up to date and able to repair your vehicle right the first time.

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