How To

HOW DO I...Understand trouble codes?

You’re driving along, all seems well, and suddenly your “check engine” light comes on.

You’re driving along, all seems well, and suddenly your “check engine” light comes on. Nothing else has changed; your vehicle is operating exactly the same as it has for years. How critical is it to deal with this right away? Will I damage my car if I keep driving?

The general answer is that you can continue to keep driving, although it would be advisable not travelling further than necessary without having it checked out. The MIL (malfunction indicator light) is an amber light, not a red one, because the urgency and risk of continued operation are relatively low, and its primary purpose is notifying you of a fault that could cause increased emissions.

Exceptions to this “carry on” advice include if the light’s presence is accompanied by a change in behaviour (like vibration or reduced power) or additional lights/messages. A flashing MIL also indicates that there is a misfire that can potentially damage your catalytic converter(s). Driving with a misfire can quickly melt or break up the ceramic honeycomb that’s inside the converter(s).

Since 1996 automakers in the U.S. and Canada have been required to use both a standardized data-link connector (DLC) and diagnostic trouble code (DTC) protocols determined by the SAE (Society of Automotive Engineers).

Because of this standardization, basic code readers that plug into your car’s DLC are inexpensive and widely available. Even so, what the reader tells you isn’t always going to be straightforward, and it may not give you the entire picture.

It’s important to understand that just because a code’s definition spells out a specific component, that component may still not be the culprit. A split or loose intake air duct can set a mass airflow sensor code, for example.

While common failures certainly exist, remember that the internet is chock full of information, both accurate and inaccurate. An inexpensive part might be worth a Google gamble, but what about a $400 airflow sensor?

Having a trusted repair facility advise you on the potential severity of the fault is your best play.

Brian Early is a longtime Wheels contributor and a Red Seal automotive technician with over 25 years experience.

Wheels Logo
Show Comments