What happens if I ignore a check engine light?
Immediate risks
If the check engine light is flashing, stop driving as soon as it's safe. A flashing light means a severe misfire is occurring, which can dump raw fuel into the exhaust and overheat the catalytic converter, leading to expensive damage. Even a steady light can indicate a problem that affects emissions or drivability. In some states, a check engine light will cause you to fail an emissions test.
- Flashing light: stop driving, risk of catalytic converter damage
- Steady light: can often be driven, but diagnose soon
- Failed emissions test in many states
- Potential for reduced fuel economy
Long-term consequences
If you ignore a steady check engine light, the underlying issue can worsen. For example, a faulty oxygen sensor can cause the engine to run rich, which eventually clogs the catalytic converter and costs over $1,000 to replace. A small vacuum leak can lead to lean conditions that cause misfires and engine damage. Ignoring a transmission code might result in a costly transmission failure. In short, small problems often become big, expensive ones.
What to do
Get the codes read with an OBD-II scanner. Many auto parts stores will do this for free. Once you have the code, you can research the likely causes or take the car to a trusted mechanic. Don't just clear the code and hope it stays off; if the problem is still present, the light will come back. Addressing the issue early usually saves money and keeps your car running cleanly.
- Read codes with an OBD-II scanner
- Research the code or consult a mechanic
- Don't just clear the code without fixing the issue
- Repair early to avoid bigger bills
Common mistakes
- Thinking a steady light is always safe: it may indicate a problem that can strand you or damage expensive components.
- Clearing the code without fixing it: the light will return, and you may miss a chance to catch a developing issue.
- Assuming it's just a sensor: sometimes a check engine light is triggered by a loose gas cap, but other times it's a serious engine fault.
