Check Engine Light Codes FAQs

Check engine light codes are set when your car’s computer recognizes a fault or failure within a component or sensor in the engine system. The check engine light may come on for something as simple as a loose gas cap or as complex as a bad computer.

Codes can be read and reset easily at any reputable auto repair shop as well as most parts stores. Keep in mind that once the check engine light codes are read, it’s not necessarily best to replace a component simply because a fault code may relate to it. For example, an oxygen sensor fault code could set because of a leaking vacuum hose. The $2 vacuum hose repair is pocket change when compared to replacing the oxygen sensor at a cost of $100 to $150.

Check engine dash warning light onComputers constantly cycle through individual system checks each time you drive your vehicle. This is usually the reason for check engine light codes that turn warning lights on and off intermittently. Computers are programmed to send a warning when problems (faults) are identified during a specific set of driving conditions. The next time you drive the vehicle, it may not duplicate that particular set of driving conditions, so the computer does not detect the fault and no dash warning light is displayed.

When this happens, retrieving fault code history from your vehicle’s computer may show a code has been set even though it is not currently displaying. A skilled repair professional needs to diagnose the cause of the fault code before the proper repair can be identified.

Why does a loose gas cap turn on my check engine light?
One job of your car’s computer to test the fuel system for any leaks in the evaporative system designed to capture gas fumes. Leaks allow raw fuel fumes to move into the atmosphere and contribute to smog. Because a loose gas cap can be a source of leaking fumes, the computer tests for an airtight system and sets a warning light when a leak is detected.

Is it a problem if a parts store erases or resets a fault code before I go to my mechanic?
When a vehicle arrives at a shop, there are two ways to pinpoint problems that cause check engine light codes. One is to clear or reset the code and drive the car to see if the fault recurs and the light comes back on. The other is to read the code and follow the diagnostic charts to pinpoint the cause of the fault.

When the code is cleared at the parts store, your mechanic will not be able to read the code and therefore cannot diagnosis the problem. If you record the code number and description retrieved by the parts store personnel, a technician at your repair shop can use that information to check the car over for obvious causes that relate to the particular fault code.

Do I need to stop driving as soon as I see a check engine warning light appear?
When your vehicle’s computer finds one or more faults and check engine light codes are set, a warning light on your dash turns on to notify you. If your vehicle still seems to start and run normally, you can keep driving but remember to call your repair shop and schedule an appointment to diagnose the problem.

What should I do if the check engine warning light is flashing?
If the check engine light starts flashing while you are driving, do the following:
1. Find a safe place to pull over.
2. Shut the car off completely.
3. Restart it after a few minutes.
4. If the light remains off, resume driving and schedule a diagnostic appointment to find out why the lite was flashing.
5. If the light begins flashing again, find a safe place to stop as soon as possible and arrange to have the vehicle towed to a reliable automotive repair shop like Tune Tech Downtown.

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