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Anyone who can think critically and logically to evaluate situations is considered very desirable by the industry. Critical thinking is the art of being able to judge or evaluate something without bias or prejudice. When diagnosing an automotive problem, critical thinkers are able to locate the cause of the problem by responding to what is known, not what is supposed! Good critical thinkers begin solving problems by carefully observing what is and what is not happening. Based on these observations, something is declared as a fact. For example, if the right headlamp of a vehicle does not light and the left headlamp does, a critical thinker will be quite sure that the source of the problem is related to the right headlamp and not the left one. Therefore, all testing will be centered on the right headlamp. The critical thinker then studies the circuit and determines the test points. Prior to conducting any test, the critical thinker knows what to test and what the possible test results would indicate. Critical thinkers solve problems in an orderly way and don’t depend on chance. They come to conclusions based on a sound reasoning. They also under stand that if a specific problem exists only during certain conditions, there are a limited number of causes. They further understand the relationship between how often the problem occurs and the probability of accurately predicting the problem. Also, they understand that one problem may cause other problems and they know how to identify the connection between the problems. Solving problems is something we do every day. Often the problems are trivial, such as deciding what to watch on television. Other times they are critical and demand much thought. At these times, thinking critically will really pay off. Although it’s impossible to guarantee that critical thinking will lead to the correct decision, it will lead to good decisions and solutions. Diagnosis The word diagnosis is used to define one of the major duties of a technician. Diagnosis is a way of looking at systems that are not functioning properly and finding out why. It’s not guessing, and it’s more than following a series of interrelated steps in order to find the solution to a specific problem. Solid diagnosis is based on an understanding of the purpose and operation of the system that is not working properly. In service manuals there are diagnostic aids given for many different problems. These are either symptom based or flow charts. Flow charts or decision trees --- guide you through a step-by-step process. As you answer the questions given at each step, you are told what your next step should be. Symptom-based diagnostic charts focus on a definition of the problem and offer a list of possible causes of the problem. Sometimes the diagnostic aids are a combination of the two-a flow chart based on clearly defined symptoms. When these diagnostic aids are not available or prove to be ineffective, most good technicians con duct a good visual inspection and then take a logical approach to finding the cause of the problem. This relies on critical thinking skills as well as sys tem knowledge. Logical diagnosis follows these steps: 1. Gather information about the problem. Find out when and where the problem happens and what exactly happens. 2. Verify that the problem exists. Take the vehicle for a road test and try to duplicate the problem, if possible. 3. Thoroughly define what the problem is and when it occurs. Pay strict attention to the conditions present when the problem happens. Also pay attention to the entire vehicle; another problem may be evident to you that was not evident to the customer. 4. Research all available information to deter mine the possible causes of the problem. Try to match the exact problem with a symptoms chart or think about what is happening and match a system or some components to the problem. 5. Isolate the problem by testing. Narrow down the probable causes of the problem by checking the obvious or easy-to-check items. 6. Continue testing to pinpoint the cause of the problem. Once you know where the problem should be, test until you find it! 7. Locate and repair the problem, then verify the repair. Never assume that your work solved the original problem. Make sure the problem is history before returning it to the customer. -- A symptom-based diagnostic chart. Symptom; Probable cause; Remedy; Engine won’t start; or Vacuum hose disconnected; Repair or replace; hard to start or damaged EGR valve is not closed-- Repair or replace Malfunction of the EVAP-- Repair or replace Canister --Purge Solenoid Valve --Repair or replace Rough idle or engine --Vacuum hose disconnected --Repair or replace stalls or damaged EGR valve is not closed --Repair or replace Malfunction of the PCV valve --Replace Malfunction of the EVAP-- Check the system; if there is a Canister Purge-- System problem, check its component parts --Excessive oil --Positive crankcase --Check positive crankcase consumption ventilation line clogged ventilation system-- Poor fuel mileage Malfunction of the exhaust --Check the system; if there is a gas recirculation problem, check its component parts Next: Professionalism; Interpersonal Relationships Prev.: Automotive Technician: On-the-Job; Communications Home Article Index top of page |
