Audio By Carbonatix

Buying a used car can put concerns like bloated price tags and depreciation out of the equation. However, it can introduce you to a world of title and maintenance concerns. Fret not, though, brave bargain hunter. This tenured mechanic shows how a scanner and a little know-how can spare you from a “very big expense” or two.

A Georgia mechanic recommends that shoppers hunting for used cars scan their would-be purchase and look for the monitors

Granted, used car shopping is a bit of a gamble. Sure, it’s never been easier to look up a vehicle’s title status and accident history. But you can still drive off the lot looking at a clear gauge cluster, just to have that soul-sapping check engine light rear its ugly head. This seasoned mechanic, however, says you can take charge to “avoid a very big expense” down the road.

The Georgia mechanic describes an instance where you purchase a used car, and the check engine light illuminates not long after you drive your treasured wheels away. “Was that on before, and someone cleared it? We don’t know.” It’s true. A dealer or prior owner can clear codes, leading to a veritable time bomb of a headache. 

But there’s something you can do about it. “When the system is cleared of codes, it clears what we call the monitors,” he said. “When they clear the codes, it goes to ‘incomplete.’ What we’re looking for is a set of complete monitors.” To search for the monitor statuses, he used a Bluetooth-enabled OBD II port scanner. A glance at the monitor values reveals a cascade of “complete” and “not available” values. 

“We’re not worried about ‘not available,’” he said of the latter. “The big one that we’re looking for is the catalyst monitor. That one takes the longest to run.” So, in theory, if someone cleared that code, it would take quite a bit of road time for the monitor to recognize that the issue still exists and flash a code. “If that one says ‘complete’ and the rest of them say ‘complete,’ you’re probably okay. They didn’t clear the codes.”

He then dips into the cabin of another used car, a Toyota, to demonstrate a bad egg, as it were. The mechanic attached the Bluetooth scanner tool and cleared the three existing codes. Then, to show off what car buyers should be looking for, he turns the car on and opts for the live data function. Sure enough, the EVAP monitor and dreaded catalyst monitor read “incomplete.” 

Now, the mechanic suggests that a shop might tell you that they’ve repaired an issue, and the monitors haven’t had enough road time to evaluate and update. Be that as it may, he hazards against driving off the lot with a car in that scenario. “You don’t want to buy it until those monitors are done.”