Technical 18 Find evidence: The foundation of every successful diagnosis In the first of a series of articles, Darren Quinn from Mechanic Mindset takes us through his ‘FIXDIT’ framework, designed to provide a simple, memorable way to apply the critical stages required for a successful diagnostic routine. This month, we explore the first stage, ‘Find evidence’, with future issues set to cover the subsequent stages: ‘Inspect evidence’, ‘eXecute diagnostic plan’, ‘Determine the cause’, ‘Implement repair’, and ‘Test’. Successful diagnostics has never been about luck. The best technicians follow a process. Whether diagnosing an intermittent electrical fault, a drivability issue, or a complex network communication problem, the same fundamental stages must be followed. The challenge is that many technicians don’t consistently apply them. Steps are skipped, assumptions are made, and testing begins before the problem is fully understood. So it is essential to start with the foundation of every successful diagnosis: ‘Find evidence’. Before testing begins When a vehicle arrives with a fault, most technicians feel an immediate urge to start testing. Scan tools come out, fault codes are checked, and measurements begin. It feels productive. It feels like diagnostics. But in many cases, the biggest diagnostic mistake occurs before a single test lead is connected. The mistake is failing to gather enough evidence. Modern vehicles are incredibly complex. A single customer complaint may involve multiple control modules, network communications, software strategies, environmental conditions, and intermittent operating states. If technicians begin testing without first fully understanding the problem, they risk heading down the wrong path from the very beginning. At Mechanic Mindset, we teach that diagnostics is not a process of testing first. It is a process of investigation first. Start with questions One of the most valuable sources of evidence is standing right in front of you: the customer. Unfortunately, this is often the most overlooked part of the diagnostic process. In a busy workshop, conversations can become rushed. Customers may be interrupted, assumptions are made, and important details are missed. Professional technicians understand that customer questioning is not administration. It is evidence gathering. Consider two different approaches. “Does the engine warning light come on all the time?” Or. “Can you explain exactly what happens when the problem occurs?” The second question encourages the customer to provide context, timing, conditions, and observations that may never emerge from a simple yes-or-no answer. Intermittent faults particularly depend on this information. A customer may reveal that the fault only occurs after motorway driving, during heavy rain, when towing, or on cold mornings. These details can dramatically change the direction of the diagnosis. The goal is not simply to hear the complaint. The goal is to understand the circumstances surrounding the complaint. The vehicle has a story The second source of evidence is the vehicle itself. Before reaching for advanced test equipment, technicians should perform a thorough initial inspection and complete a function test. Many faults leave clues long before any measurements are taken. A full function test is about far more than simply confirming the customer’s complaint. Professional technicians assess all related systems and record both what is working and what is not. This is important because systems that operate correctly can often be just as valuable as those that have failed. For example, if several electrical systems are inoperative while others continue to function normally, that information can help identify common power supplies, grounds, modules, or network pathways that remain
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