“My Check Engine Light is on”… “How much to plug it into your thing and tell me whats wrong”

Posted: February 4, 2012 in Uncategorized
Tags: , , , ,

Ah the elusive check engine light. A common source of misinformation for the public fueled by the dollar-store parts houses that freely imply that selling a part associated with a trouble code will fix your problem without any sort of liability or responsibility for being right or WRONG!

The TRUTH: like to hear it, here it go

Yes our cars have these pretty impressive and advanced computers inside them that continuously watch what every little sensor and do-dad are doing at any given millisecond. But while they are so very intelligent, the error codes that they save in memory when something isn’t quite right are anything but acute condemnations of any specific part. These code are not a self-diagnosis of the vehicle. They are but a mere trail of breadcrumbs designed to point a trained technician in the area or subsystem where the malfunction lies.

Don’t get me wrong, I think its great that “code readers” have gotten so cheap that practically every corner store can hook up and at least read you the numeric trouble codes stored in your system. I also believe that every shop, parts store, and public library (maybe not the last one) should be able to at least read and tell you what the trouble codes are that are stored in your computer for absolutely no charge whatsoever. You heard me, hook up and read codes for FREE! The question remains, is this the same thing as ‘diagnosing’ the problem? Why do auto shops still have diagnostic fees and rate when I can get codes read for free at so many locations. Aren’t the parts-guy and auto-shop mechanic doing the same thing? Short answer, no. Furthermore let me answer the question with a question,  if the ‘diagnostometer’ behind the counter at Autozone is worth say $60 and I paid in excess of $25,000 for my collection of ‘diagnostometers’ and continue to pay thousands per year to keep them current, do you find it likely that we are providing you the same service?

Here is a typical scenario… An unsuspecting customer stops into their local discount parts outlet and tells the parts guy “My check engine light is on and I don’t know what to do”. To this the parts guy responds by grabbing his hand dandy $60 budget code reader, hooks it up to the standard on-car connector and voila! “Ma’am, you see here it says you need a new oxygen sensor” as he points to the display reading Trouble Code PO135, Oxygen Sensor Heater Circuit Malfunction. He adds “come on inside and I can sell you a new oxygen sensor to fix the problem”.


What if… He sells her an oxygen sensor and it doesn’t fix the problem… Maybe he even told her about a buddy of his who would put it in for her. For the argument’s sake lets say it all goes swimmingly up until the point where the sensor has been replaced, the parts guy and his buddy have been paid, but the light is still on! Sure maybe they all got lucky and the car was back to normal, no warning light, no more symptoms a victory for the amateur. But what about the other 77% of cases? Money gone but problem still here…

Lets take a step back, the complete code read “heater circuit malfunction”. If I remember back to my high school science I remember that a circuit can contain a whole bunch of things like, a power source, switches, resistors, and other junk like that. The word circuit seems to imply that there is a problem lying somewhere within a system of do-dads. Alas we have our breadcrumbs. At this point the course of action with the least amount of risk and needlessly replaced parts is to have a trained technician (we actually went to school for this stuff) follow a published set of tests and procedures recommended by the manufacturer to see which do-dad in the system is out of whack. Modern vehicles are piles of do-dads stacked on top of do-dads and all crammed into your engine compartment. It simply takes time to peal apart the layers to test each step that Honda, Toyota, or whatever manufacturer wants us to test to ensure proper repair of your car.


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