Island Vehicle Care

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Should you pay for diagnostic time or have somebody guess what the problem is?


An accurate diagnosis leads to a repair that solves the problem; therefore the diagnostic process needs to be precise and efficient.  This can only be carried out by a trained professional otherwise people are just guessing what the problem is, wasting time that is charged to you and replacing parts that are not the cause of the problem, again charged to you.

The diagnostic process (Step one) begins by extracting the SYMPTOMS from the customer, often the customer wants to say what they think is the cause of the problem i.e. 'it's probably just a fuse' or 'the carb needs cleaning' (please note - modern cars do not have carburettors, this is 20th century technology that has been overtaken with fuel injection systems).

When you visit the doctor would you tell them what you think is the cause of your ailment or would you tell them where it hurts?  It is the same diagnostic principle with your vehicle except the technician has the advantage of experiencing the 'symptom' themselves and this is the most important part of the first step.  If any further action is taken without verifying the customers' symptom then this is a guess or an assumption and you are risking unnecessary time and cost.


Step two is to verify if any related systems are also displaying signs of malfunction i.e. carrying out a road test to ‘feel’ for other unusual activity, or activate other related systems that may also be malfunctioning that have not been noticed by the customer, a diagnostic scan of your vehicle computer network may also be required during this step if a warning light is activating.

Step three is to analyse the data collected so far, at this point the technician needs to decide which area the symptoms are pointing towards.  Further research relating to the symptoms and data may be required, this step may only require a few seconds if the problem is visual or audible i.e. an oil leak or a knocking noise from underneath, or may take longer if diagnostic manuals or wiring diagrams need to referenced.

Step four is to isolate the trouble; this could be something simple like a visual inspection with the vehicle either on the ground or lifted in the air, components may need to be removed, or more involved methods may be required using specialist diagnostic tools to obtain more electronic data or results.


These steps so far will reduce the time needed to accurately diagnose the problem and requires the technician to be trained and knowledgeable about how the systems operate and interconnect within your vehicle.

Following an efficient diagnosis a repair or parts replacement can be carried out.  Afterwards it is extremely important  to VERIFY the repair, this requires taking time to perform a quality control check before returning the vehicle to the customer which involves carrying out a road test and activating systems.

Studies show that one in three service visits require a return visit to correct the problem, often something may not be tightened fully or has been left unplugged, incorrect diagnosis may have been carried out, or there may be another problem that requires attention that was not noticed during the diagnostic steps.


Taking the time to perform a quality control check will reduce the chance of a ‘comeback’ and improve customer satisfaction.

If your vehicle has a problem, click here to get it diagnosed by an Advanced Automotive Engineer.