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Automotive Column 50 Check Gas Cap

Automotive Column 50 Check Gas Cap

Syndicated Newspaper Column

One of the most common codes we see on any vehicle in our repair shop and one of the most common for our listeners is the check gas cap code or Evaporative Emissions system code. Many shops as well as customers really don't like this often misdiagnosed light.



Daily Car Repair and Advice Tips Question 50 My Check Gas Cap Light Is On

Dear Motor Medics,
I hate check engine lights! Well, maybe not so much the light as what it represents…money. They should call it the check your bank account light because every time it comes on I have to check my account to see if I can afford to turn the light off. My most recent experience involves several tries at a repair myself instead of a professional with no luck. The dash on my 2005 Deville said check gas cap so I checked it and cleared the code with one of those do it yourself readers then it came back on. Then I bought a new cap and it came on again. The code says small leak when I read it with my do it yourself scanner. What should I do next? I tried to save money but I’m no mechanic.

Dan in Sterling Illinois

Dan, I am a professional mechanic and I feel your pain. This is one of the engine codes that is best left to a shop. They sometimes pull their hair out on this one. By all means start with checking the cap and replace it if it’s worn. That’s what we do. Next we use a special machine to smoke test the vent system for leaks and repair as needed. While smoke checking we are looking for external leaks from the tank and lines and also leaks past the vent valve and purge valves. Either one will cause the code.

Take care, the Motor Medics

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Advice given by the Motor Medics is for entertainment only. Each problem is different and requires different approaches and answers given here are opinions and just one possibility. In order to make an accurate diagnosis a qualified technician should make a hands-on diagnosis. Always follow all recommended safety procedures and consult with your own qualified technician before attempting repairs of any kind.

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