3 Common Causes of Lean Check Engine Lights

The check engine light on your vehicle's dashboard may light up in case the engine is running lean (too little fuel in the fuel/air mixture). This article discusses some of the factors that may trigger the lean codes to be registered by your vehicle's control systems.

Dirty Mass Airflow Sensors The MAF (mass airflow) sensor measures the volume of cool air that is entering the engine through the cold air intake system. This sensor can become clogged with dirt in case the air filter was improperly installed to the extent that the filter didn't adequately cover the MAF sensor. Dirty MAF sensors can send inaccurate data about intake air to the engine control module. Consequently, the check engine light may come on due to an inaccurate interpretation of the amount of fuel needed to mix with the air monitored by the defective MAF sensor. Cleaning or replacing the sensor can rectify the problem.

Vacuum Leaks The lean codes can also be triggered by a leakage within the vacuum needed during the operation of the engine. Vacuum hoses, intake and manifold gaskets can allow air to leak into the engine during the combustion cycle. That excess air can upset the delicate balance of the air/fuel mixture that has been formulated by the engine control unit. The check engine light will therefore come on in response to the persistent availability of excess air during the combustion process. Checking the fuel trim values using a fault code scanner can reveal any leaks that are causing the air to be more than is required during combustion in the engine.

Inadequate Fuel Delivery Defects in the fuel delivery system can also trigger the lean error code in your car's engine. For example, the fuel filter may be clogged to the extent that very light fuel can flow through it. Alternatively, the fuel pump may not be working properly due to limited electrical power reaching it from the battery. Fuel pressure regulators can also leak and affect the volume of fuel that reaches car engines. The fuel delivery system therefore needs to be inspected and tested carefully so that the exact cause of limited fuel flow can be identified. As you can see, your car engine can run lean for a variety of reasons. It is therefore unwise for you to attempt a DIY diagnosis when you see the check engine light on your dashboard. Take the vehicle to specialists so that they can conduct thorough investigations of that problem. The problem will be fixed and the vehicle systems will be reset so that you don't keep seeing the light after the defect has been resolved.