Man talking(l+r), Mechanic working on engine(c)

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‘They’re wondering why that is’: Mechanic explains why your check engine light could be going on and off

'My 2010 grand caravan does this.'


Parks Kugle


Posted on Mar 13, 2024   Updated on Mar 15, 2024, 2:25 pm CDT

Asking for advice can be difficult in real life. Fortunately, with countless videos of mechanics sharing insights like common issues with Buicks, the biggest scams in the auto repair industry, and their opinions on different makes and models, learning about cars and repairs has never been easier.

Royalty Auto Service (@royaltyautoservice) already has over 572,000 followers on TikTok for its wide selection of videos like “Used Vehicle Advice.” Now, a mechanic at the Georgia-based company has gone viral for a clip answering a commenter’s question about why their check engine light goes on and off without them having anything fixed.

The video begins with the user’s question. “This person says their check engine light goes on and off, but they haven’t had anything fixed,” a man off-camera said. “They’re wondering why that is.”

“So you have an intermittent failure,” the mechanic responded. “What happens is the engine control module is going to constantly be running tests on these components. It’s trying to get it to pass.”

The mechanic continued to explain the issue in a straightforward manner. As he put it, the car’s computer continually tests all the systems. If the car detects an issue, it sends a code, which can set off the check engine light. The code is specific and is used to diagnose the problem at a repair shop. But, if the car tests the same system a couple of days later and the weather or driving conditions have altered, the computer may not detect the same issue, and the check engine light will go off.

According to Repair Pal, intermittent car problems can be difficult to diagnose. This is because these problems may not present themselves when the vehicle is brought to a mechanic. Overall, the problem involves the computers that control the engine, transmission, climate control, and infotainment systems. Since the computer is continually testing the system, the mechanic may need to conduct multiple tests to pinpoint the issue.

“Generally, what’s happening is something is intermittently failing, and sometimes the engine module is able to test it and is able to pass, and it turns the light off,” the Royalty Auto Service mechanic elaborated.

@royaltyautoservice Replying to @LeiaSpins Hopefully this helps you and others who have wondered about this! #checkengine #carproblems #cartok #mechanic #mechaniclife #autorepair #automotive #tips #viral #fyp #foryou #trucktok #advice #help ♬ Storytelling – Adriel

Community Auto suggests that drivers pay attention to several factors when trying to figure out what may set off the intermittent problem. These include the weather, how often the car was driven that day, how long and fast you were driving, and whether the A/C, lights, or radio was on. However, for the issue to be properly diagnosed, the mechanic will need the problem to occur at least two times while it is in the shop.

“There’s going to be a code in it,” the mechanic continued. “Just because the light goes off doesn’t mean the code goes away. Light can go off; code will still be in there for a fairly long time, so they’ll still have an avenue to go down and see if they can’t determine what’s wrong with it.”

“That’s why we always test drive multiple times—because you just don’t know. You gotta let it test a few times … and some systems don’t test all the time. Lots of different scenarios,” he concluded.

The video has been viewed over 640,000 as of publication. Viewers asked some questions of their own in the comments section.

“With today’s technology, why not just use the big ole display to tell the owner what it detected? Maybe it’s a simple fix,” one wondered.

“Just got an oil changed but the check engine oil comes on why does it does that?” another asked.

Others were grateful for their continued advice.

“Love you guys – great information. Thank you. I’ve learned so much,” a viewer said.

“Love this guy,” a second agreed.

The Daily Dot reached out to Royalty Auto Service via contact form for further information.

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*First Published: Mar 13, 2024, 5:00 pm CDT