Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that your car's computer thinks the engine is not getting enough fuel when you press the gas pedal hard, like when you're going uphill or speeding up quickly.
The engine control module (ECM) detects that the air-fuel mixture is too lean (not enough fuel) when the engine is under a higher load on Bank 1.
A P21FC code indicates that the ECM has detected a lean condition in the fuel control system for Bank 1, which means the air-fuel mixture has too much air and not enough fuel. This typically occurs when the engine is under higher load conditions, such as during acceleration or climbing a hill. This can be caused by issues such as a vacuum leak, a faulty fuel injector, or a malfunctioning mass air flow sensor.
• Check Engine Light is on
• Poor acceleration
• Engine may run rough
• Vacuum leak
• Faulty fuel injector
• Malfunctioning mass air flow sensor
ECM: Engine Control Module, the computer that controls engine functions.
Bank 1: The side of the engine that contains cylinder 1 in a V-type engine.
• Check for vacuum leaks in the intake system.
• Inspect the fuel injectors for proper operation.
• Test the mass air flow sensor for faults.
• Repair any vacuum leaks found.
• Replace faulty fuel injectors.
• Clean or replace the mass air flow sensor.
• OBD-II scanner
• Vacuum gauge
• Multimeter
$150 - $500
Moderate
• Toyota Camry
• Ford F-150
• Honda Accord
• Regularly inspect and maintain the intake system.
• Use quality fuel and fuel additives.
• Perform routine maintenance on fuel injectors.
Engine Performance
• Avoid driving with a heavy load until the issue is resolved.
• Seek professional diagnosis if unsure about repairs.
Check if the vehicle's powertrain warranty covers fuel system issues.
This code has been associated with issues in vehicles experiencing fuel economy problems and poor engine performance under load.
Moderate – It should be addressed soon to avoid potential engine damage.
Driving with a lean condition can lead to increased emissions and potential engine damage. Address promptly.
• Engine at operating temperature
• Vehicle under load (e.g., during acceleration)
The components involved are typically located in the engine bay, including the intake manifold, fuel injectors, and mass air flow sensor.
Q: Can I drive with a P21FC code?
A: It's not recommended to drive for long periods with this code, as it can lead to engine damage.
Q: Will a P21FC code affect fuel economy?
A: Yes, a lean condition can negatively impact fuel economy and engine performance.
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Fitment Required · Vehicle-fitment part
Relevant for airflow, fuel-trim, and intake-metering faults after confirming the sensor is actually at fault.
Airflow and fuel-trim codes can involve the mass air flow sensor after proper diagnosis.
Verify the sensor design and fitment for your exact vehicle.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.