Last updateWed, 18 Oct 2017 10am

On The Road

What to do about that check-engine light


Q: Can you explain why there are so many different ads out there that announce different prices – some even free – for check engine light diagnostics? And how important is it to bring your car to a shop when the light comes on?

A: The check engine light performs an important service and should not be ignored. It is telling you that there is something out of sync within your car’s emissions systems that needs to be addressed. If your check engine light is on when you need to have your smog certificate renewed, it will be an automatic failure.

The service to diagnose why your check engine light is on can only be performed correctly if the shop has invested in the right equipment, the right software and trained technicians with access to the right information to determine the cause of the warning light.

The equipment and software must be updated every year, and that is done at great expense to the shop owner. Technicians must have at least 40 hours of training each year to remain current on the knowledge required to interpret the information accumulated from the diagnostic equipment. The shop pays ongoing fees for the information.

The only information provided by the vehicle’s control unit is an error code with a definition, and this error code only points to the vehicle’s particular system. The technician must then determine which component or components within the system have malfunctioned. The repair can only take place after this step is accomplished. Anyone without the knowledge and equipment is just guessing at the correct repair.

The danger of this guesswork is that if the cause of the warning light is not repaired correctly, additional damage may occur to other components in the vehicle.

So, make sure the facility you take your vehicle to for this type of repair has the ability to do it correctly.

If the first step in the process (determining why the light came on) is not being charged for, or if it is a minimal charge, then it usually means there has been no investment in the correct equipment, software or training. If that’s the case, the outcome of any subsequent repair may not be what you expect.

Sometimes the code is pulled, but then you are asked to spend more money to dig deeper into why the code was triggered. Even worse is when the code is pulled and you receive a diagnosis, but the diagnosis is wrong because of lack of knowledge or incorrect equipment.

You may think you are saving money by responding to an ad for an inexpensive check engine light repair, but you could end up with more problems than you had in the first place.



Warren McCord is an ASE certified master technician and owner of Dean’s Automotive Inc., 2037 Old Middlefield Way, Mountain View. For more information, call 961-0302 or e-mail McCord at This email address is being protected from spambots. You need JavaScript enabled to view it..

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