Why Your Check Engine Light Might Be Costing You Power

A check-engine light isn’t just a warning — the fault behind it often costs power and fuel. Here is why, and what to do.

How a Fault Costs Power

• Sensor faults (oxygen, mass airflow, coolant temperature) make the ECU run on default values, usually richer and more conservative.
• Misfires waste fuel and can overheat the catalytic converter.
• Limp mode: on serious faults the ECU limits power or holds a gear to protect the engine.
• Boost leaks on turbo engines cut power sharply.

What to Do

1. Read the code. Any OBD-II reader will do. A flashing light means an active misfire — stop driving hard and get it checked.
2. Fix the cause, not the light. Clearing a code switches the light off until the fault returns.
3. Check the basics: gas cap, air filter, spark plugs, vacuum hoses.

Tuning and Check-Engine Lights

Fix faults before tuning: a calibration can’t make up for a failing sensor. Monte stays within factory sensor ranges and doesn’t disable any system, so it shouldn’t set a light; in independent bench testing at SEMA Garage no codes were set. If a light ever appears with Monte installed, unplug it — the car returns to stock straight away — and contact us.

Monte GTR has a built-in code reader that reads and clears fault codes on its own screen. More about OBD-II diagnostics →