Sometimes the solution to a problem sends you on a convoluted path. Many customers believe that automotive repairs are always cut and dried. You say to your mechanic, “My car does this.” Your mechanic says to you, “You need a new that.” Simple. “How much?”
My last couple of diagnostic debacles are proof that simple can be elusive. I am the type of mechanic that prefers testing to guessing. I know there are a lot of guessers out there. The Internet seems to be designed for guessers. Many a common problem is solved by Google. As long as you know something about what you are googling.
Google “Why is my check engine light is on”. Here you will get a list of the top 5 or top 10 reasons. One will be loose cap, one will be worn spark plugs, and one will be a bad catalytic converter. Tighten your gas cap, essentially free. Replace your spark plugs, anywhere from $100 to $700. Replace your catalytic converter. Ouch, maybe $300 to $1500. I guess you will start with the gas cap.
After tightening the gas cap, the light is still on. What next? Those other two items are expensive. They are not worth the guess. Time to get a professional involved. Instead of a full set of spark plugs it may only be one spark plug wire. Instead of a catalytic converter it may only be a leaky exhaust gasket. Those Google stats will flush your wallet a lot quicker than any mechanic will.
There is a time for guessing and playing odds but it just doesn’t feel right to me even though I will succumb to it. I do not want to put a part on that in the end was not required. Sometimes the educated guess is the most cost effective way though. Some manufacturers even make replacing parts one of their diagnostic process steps. Usually that part is expensive and we do not have one hanging around.
Faults that only occur periodically many times require a guess. Sometimes catching an intermittent fault is extremely difficult. When the result of an intermittent fault is a vehicle that needs to be towed, the guess hopefully will save a lot of tow bills.
Sometimes the guess for an intermittent problem is an easy call to make. A particular make or model vehicle always has the same problem. Google says replacing that thing will fix it. Thousands of people concur. The pièce de resistance; your local parts distributor has the part in stock.
The real problem repairs are those where testing shows the parts that are commonly at fault seem to be working correctly. Testing shows the problem is likely a more expensive component. A quick enquiry to the dealer parts department finds that the seemingly faulty part is not available in Canada. There is one in Kansas though. The parts person says they have never sold one. That guess feels stacked against you.
What to do? This is far from cut and dried. Going against the odds!
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC.E-mail: firstname.lastname@example.org