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Q: Why does the check engine light keep coming back on?

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I have 97,000 miles on my 2006 GMC Sierra, and recently I have had to get the Check Engine light reset more than once. It first came on when some sensor went bad, but when it came back on not too long later, the mechanic looked at it and didn’t find anything. Is this going to be an ongoing problem? Is it possible that something broke when the sensor was replaced? This is my work truck so I plan on getting some more life out of it yet.

The check engine light comes on and stays on if the onboard computer sees a problem that could cause an increase in emissions or a problem with its systems. After looking at most of the possible codes or issues that could cause the check engine light to come on. The most common problem your vehicle is having is an evaporative system problem since you say a technician could not find any problems. The fuel tank evaporative system vent solenoid could be the failure because they are prone to getting dirt and debris in the solenoid filter causing them to not vent the tank properly. The valve will operate electrically.

My recommendation would be to have your computer system checked for codes relating to the evaporative fuel tank system by a qualified mechanic. A certified mechanic with YourMechanic can inspect and diagnose the fuel tank system at your home or office. The fix recommendation would be to replace the evaporative vent solenoid and the fuel tank cap.

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