We have libraries of stories of where the miss-interpretation of information stored in the vehicles on board computer resulted in needless expense.

Many parts stores now offer “free diagnostics”. This free service usually involves interfacing the on board computer, downloading the stored codes, and then the codes are cleared from the computer. The salesperson then informs the customer of the code. The codes may be “misfire on cylinder #3” and “bank 2 oxygen sensor”. Based on this information, a sale is typically made (perhaps a set of plugs and an oxygen sensor). The reality may be that neither part will fix the problem.

Why would only one of the 6 spark plugs fail? How can an oxygen sensor fail on only one bank of the exhaust system, and yet the other bank is fine? Both are great questions that a true Technician would ask, and find the answer to. If a head gasket was failing it could create a condition in the #3 cylinder that may cause both the plug to fail, and the oxygen sensor to read strange readings, and replacement of plugs and the oxygen sensor, will not fix the problem. Replacing these parts will however cost money and will ultimately result in replacing those parts--again, when they fail again.

The worst part is, in this example, the engine may be permanently damaged because the real problem was not realized until too late. Sure, the oxygen sensor, and plugs were less money than the gasket repair job, but ultimately they were not the best use of those hard earned dollars.

That is an extreme example of why you deserve the very best in automotive repair.