Check Engine Lights – A Crash Course

MINT HILL, NC – Check engine lights. That big orange light that everyone is afraid of. But should we be? Check engine lights are a unique tool that has revolutionized how we inspect, maintain, and keep cars running.

The check engine light as we know it today was born in the mid-1990s. These check engine lights are part of the OBDII system. OBDII is short for onboard diagnostics II, but the name itself is a bit misleading. There was never a standardized “OBDI.” Through 1995, each manufacturer determined how a check engine light and its trouble codes would work. Codes weren’t standardized and could change from one brand to another. We refer to the modern incarnation as OBDII simply because it simply replaced something that had previously been semi-unregulated, and because it needed to be differentiated from what had already been in use.

From 1996 to today, all cars sold in the USA have OBDII equipped. It standardizes why a check engine light can come on across-the-board and makes diagnosing vehicles easier. It can come on not just for mechanical malfunctions, but for pollution issues and electrical malfunctions too.

This light commonly either takes the shape of an engine or is the text that says “SERVICE ENGINE SOON.” Wrench, maintenance, ABS, VSC, TPMS, and Traction Control lights, while important, are no check engine lights. Check engine lights are designed to primarily focus on the powertrain and emissions, not suspension, handling, or tires.

A lot of times I’ll get asked “is pulling a Check Engine Light Code diagnostic?” and the answer to that is no. Codes, while great for pointing you in the right direction, are not diagnostic. Example: Let’s say your check engine light comes on and it’s a P0456 – Small EVAP Leak Detected. Simple right? Not quite. EVAP is short for an evaporative emissions system. This system has lots of different parts involved. The charcoal canister, canister vent valve, purge solenoid, purge valve, vapor lines, and your fuel tank are just some of the parts EVAP systems. Did that code tell us which of these things went bad? What if nothing is bad at all, and your vehicle’s computer (PCM) isn’t testing correctly causing a false-positive?

We don’t know, and we can’t until we dig a little deeper. That is diagnostic. Codes are helpful, they steer us in the right direction, but they aren’t genies in a bottle.

Remember, OBDII was implemented in 1995 and hasn’t changed much. Do you have a smartphone, or a fairly new Mac, or a Windows 10 PC? You know what those are capable of, right? Well, your car is running the automotive equivalent of Windows 95. While there is better tech out there, it hasn’t been federally mandated yet. So until that day comes, OBDII is the path we’re going to take.

Ken Manchester