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How do we diagnose complex "issues" when they go wrong?

Often, when an appliance stops working, we don't even think about repair; we simply purchase a new one -- there is limited or no diagnosis involved.

We may check to make sure everything is plugged in, that a circuit breaker hasn't tripped, or even check the internet to see what we find, but that's typically the extent of it.  

Think about it. For example, many microwave ovens can be replaced for less than £100, while the average cost of a repair is about £133.  That's because repairing one typically takes a technician up to an hour to diagnose and repair the problem. Plus on top of the cost for the technician's time, there is the cost of the replacement parts. Combine this with the sheer inconvenience of the repair process like schedule coordination or shipping,  and it becomes clear why this type of repair process only works for more expensive items.

We now use
state of the art Bosch KTS Diagnostic equipment!

ECU multi-functional tester with all the necessary tools for fault diagnostics in the workshop and on-the-move. It’s also ready-to-use within seconds, and is really easy to use by a modern, simple and intuitive user interface.

Equipped with ESI[tronic] including an outstanding coverage of more than 150 vehicle brands, as well as the best Bosch VIN database, automatic VIN identification and automatic online updates, the KTS 250 ensures workshops are up-to-date and at the forefront of vehicle diagnostics.

When our gas fireplace stopped working, we called a company that specializes in fireplace service and repair. The process was interesting because it brought to light an interesting concept of what they consider "diagnosis." For this particular company, "diagnosis" was simply "calling the manufacturer hotline and having them identify what should be replaced."

This was done based on symptoms.  In our case, the identified symptom was "not switching on intermittently." The answer supplied by the hotline was, "it's the electronic module." So, the £350 electronic module part was ordered. When it arrived, the technician came by to replace it, but the fireplace was working! He suggested that we call him when it fails again, "I will come by, check it, and replace the module," he assured us. 

I could not believe what I was hearing!!! This may be how automotive repair diagnosis is perceived, but it is certainly not how it's done!

Well, let me back up a bit, there might be a grain of truth to this regarding calling a hotline, but it's certainly not industry practice to call a hotline and have them tell you what to replace.Well, sure enough, it failed again, and they came by and installed the module, but it still didn't work!

The technician went back to the hotline again, and there was a new suggestion, "replace the auxiliary power supply." When I suggested to the service department that this was not a diagnostic process but simply trial and error, she gave me an automotive repair analogy. "If you took your BMW to a dealer this is what they do. They call the manufacturers' hotline, and they tell the mechanic what to repair." 

But then, what is the "automotive diagnosis process? How do we diagnose and repair a complex vehicle with dozens of mechanical systems coupled to dozens of computer modules all hooked together on a network?

The ten point diagnostic procedure relies on good communication, particularly from the customer to the technician regarding what's going wrong with the automobile. A skilled technician needs to have good "critical thinking" skills plus very good "problem solving" skills. These skills are essential because modern vehicles with dozens of computers can go wrong in an infinite number of ways.

Step One: The service writer interviews the customer and documents the symptoms on a diagnostic form.

Step Two: The technician confirms the problem, and starts with some basic checks. For example, check the battery and make sure the connections are in good condition.

Step Three: The technician then checks for any service updates related to the symptoms and system with the problem. This is where a layperson may get the idea that "If you took your BMW to a dealer this is what they do, they call the manufacturer and they say what to repair." It's true that there are "pattern failures." Things can go wrong because of a faulty batch of parts. These faults include related recalls and service updates. Once the technician is sure there are not any quick fixes he is on his own!

Step Four: The skilled diagnostic technician, reviews the system being worked on and starts a logical step by step diagnostic procedure.

Step Five: At this stage, the mechanic might call a technical support hotline, and go over the process he is using. He might share data, and the support hot line might link with the technician to work together to diagnose the problem in the most efficient way.

Step Six: Once the problem has been diagnosed the technician reports his findings to the service writer.

Step Seven: The service writer makes an estimate of what it will cost to complete the repair and calls the customer to get approval to proceed. Sometimes we find a defective part, and we have to replace it to continue the diagnosis. This could be the only problem or the first step in the diagnosis.

Step Eight: Once the problem is repaired, the technician reassembles and tests the vehicle. He saves the data in the computer. Sometimes we perform a complete electronic scan of the car and save it in the computer.

Step Nine: The service writer then finishes documenting the repair.

Step Ten: Once everything has been documented, the vehicle is given a final test drive and check before it is parked and is ready to be returned to the customer.