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Know Your Limits with Code Readers

What it tells you may not be what you think


Modern cars are kinda cool, right? If something mysterious is going on, all you have to do is plug in an OBD-II code reader and viola! you can know what’s wrong with your vehicle and get it fixed.

But all that knowledge that the code reader equips you with can also be a folly, especially if you’re an enterprising DIYer with little automotive experience.

Proceed with caution!

Lou Trottier of “The Globe and Mail” explains that he’s had two vehicles recently come into his shop with failed timing chains. Both owners used a code reader that showed an error code for the camshaft position sensor, so they simply thought their sensor needed to be replaced. While it was true that the code reader was actually detecting a camshaft that was out of position, and the reason why it was not in position was because the timing chain was stretched and needed to be replaced.

As it happened, both owners reset their computers with the idea that the problem would sort itself out with a reboot. One owner even bought a new sensor, but that wouldn’t have solved the problem because it wasn’t the sensor to begin with. As a result, both owners needed repairs that exceeded the value of their vehicles.

As Trottier explains, “Buy your $89 code readers, but know your limits,” because if you don’t understand the mechanics of an engine, you may not understand what the code reader is truly trying to tell you.

Diego Rosenberg
Diego Rosenberg
Lead Writer Diego Rosenberg is a native of Wilmington, Delaware and Princeton, New Jersey, giving him plenty of exposure to the charms of Carlisle and Englishtown. Though his first love is Citroen, he fell for muscle cars after being seduced by 1950s finned flyers—in fact, he’s written two books on American muscle. But please don’t think there is a strong American bias because foreign weirdness is never far from his heart. With a penchant for underground music from the 1960-70s, Diego and his family reside in the Southwest.


  1. I hear you, sir. I do understand, at 63 I’ve been working on mechanical stuff for over 50 years. My ’04 Tahoe needed a new engine, I sourced a later rebuilt Escalade 6.2 (still a LS/LQ engine) put on a Spectre cold air kit and converted to true dual 3″ exhaust with aftermarket cats. The ‘Slade’s computer hates it all, throws codes for failed cats, lean conditions, and emissions faults. I got tired of erasing codes to shut off the icon, and put a small piece of black tape over the light. I know what I did and why the ECU is objecting. And I keep up with my maintenance, so need no “check engine” icon. Jeezus wept, I went decades without a computer trying to tell me what to do, I think I will survive. The ‘Hoe runs great, btw. Will smoke all 4 20″ Hankooks at will. Fie on a system that tries to scare one to the dealer for a loose gas cap.


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