Preventing Over Repairing: Things To Consider

Okay, now for the subject shops never want you to read about... "Over Repairing" engine light concerns! This is my politest way of addressing misdiagnosis of the root cause of check engine lights (or any Electronic Engine Control System malfunction for that matter). Okay, I'm going to say it... it should almost never take more than one part, or wiring repair to correct those troublesome service engine soon lights. I say "almost" because there are always exceptions to every rule, and I have run across them myself (but it is very rare).

So if you find yourself being told you need a number of parts to correct a check engine light, be very wary! It is possible that time is not being taken to correctly diagnose the concern. Most times, in my experience a technician is either not fully understanding the root cause of the concern or they are blindly following a series of test steps without comprehending exactly what it is they are testing for. This is a big mistake and will often lead you to false conclusions. If you are in any type of service industry then you know that even the best manuals are often wrong, or overlook the fundamentals, assuming we have properly done all our pre-checks before starting a pinpoint test. If a technician understands what he/she is testing and why they will catch these errors every time and will then perform the additional checks for things the book may not have taken in to consideration.

Okay, to back track a little, if your engine light comes on and the vehicle is driven for 6 months or so before being looked at then there is a chance that another concern could have developed in that time, so it is always best to address check engine concerns as soon as possible. Computers in newer vehicles very rarely go bad as most of their internal components are protected from shorts by built in circuitry. I always recommend re-running your tests if your final diagnosis is deemed to be a faulty computer (also referred to as a PCM - Powertrain Control Module or ECM - Electronic Control Module). This rule has saved many technicians from a faulty diagnosis! Today's vehicle circuits are very well engineered so the chance of a short circuit damaging multiple components is slim. If your vehicle is being serviced by a shop and they insist you need multiple components, politely ask if all of the parts being recommended are required to keep the check engine light off. Some may be being recommended for other reasons, such as special service messages or TSB's (Technical Service Bulletins) that call for a revised part from the manufacturer. This does happen as manufacturers revise parts they have discovered do not perform as well as they were designed to. If they say multiple parts are required ask for the reason why each part is needed and get the specifications that are out of range. I would also request the old parts be returned to you and if you are questioning the diagnosis you could component test them yourself in many cases. A second opinion is never a bad idea but take the time to ask around and find a shop with a good reputation (or contact us!). Also remember, the manufacturing dealers often charge more, but you may actually be saving in the long run. There is no substitute for the right training and the right tools.

Most importantly we are here for you! The awesome thing about the web is that twenty four hours a day, seven days a week you can fire up your computer and check code definitions and specifications anytime, or anywhere right here at One last thing; multiple codes does not necessarily mean multiple problems. For instance if you had a faulty Mass Airflow Sensor this could cause incorrect airflow readings which would result in incorrect fuel pulse width, which may cause a lean running condition. In this instance you would likely have codes for the MAF sensor, as well as lean codes for both banks 1 and 2 from the oxygen sensors. So in this example you have 3 codes for 1 faulty component! Sorry for the technical jargon! This is where it is critical to determine the route cause of the concern. We hope you find this information useful. Be sure to check out our other informative articles, hopefully we can help take some of the mystery out of the check engine light for you, and save you a few bucks in the process. Enjoy the day!

The Team

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