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 the car's computer has detected that the engine is not getting enough fuel on one side when the car is working hard. It's like if you were trying to run fast but not getting enough air to breathe.
The P21FE code indicates that the air-fuel mixture is too lean (more air than fuel) on Bank 2 during high load conditions.
When the engine is under high load, the fuel control system is responsible for maintaining the correct air-fuel ratio. If the ratio becomes too lean on Bank 2, it can lead to poor engine performance and potential damage. The ECM (Engine Control Module) monitors the oxygen sensor readings and adjusts the fuel injectors accordingly. If it detects a lean condition that it cannot correct, it triggers the P21FE code.
• Check engine light is on
• Poor acceleration
• Engine misfires
• Vacuum leaks
• Faulty oxygen sensor
• Fuel injector issues
ECM: Engine Control Module - the computer that controls engine functions.
Oxygen Sensor: A device that measures the amount of oxygen in the exhaust gases.
• Check for vacuum leaks in the intake system.
• Inspect and test the oxygen sensors on Bank 2.
• Examine fuel injectors for clogs or faults.
• Repair any found vacuum leaks.
• Replace faulty oxygen sensors.
• Clean or replace malfunctioning fuel injectors.
• OBD-II scanner
• Vacuum gauge
• Fuel injector cleaning kit
$150 - $500
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regular maintenance of the fuel system
• Timely replacement of air filters
• Periodic inspection for vacuum leaks
Engine Performance
• Do not ignore the check engine light.
• Have the vehicle inspected by a professional mechanic.
• Avoid high-load driving conditions until the issue is resolved.
Check with the vehicle manufacturer for warranty coverage on emission-related components.
Lean condition codes like P21FE have been common in vehicles with aging fuel systems or those with unmaintained intake systems.
Moderate – It should be addressed soon to prevent engine damage.
Driving with a lean condition can lead to increased emissions and potential engine damage.
• Vehicle at operating temperature
• High load driving conditions (e.g., uphill or towing)
Bank 2 refers to the side of the engine opposite to Bank 1, typically on V-type engines.
Q: Can I drive with a P21FE code?
A: It's not recommended to drive for extended periods with this code, as it can lead to engine damage.
Q: How do I know if my car has a vacuum leak?
A: A hissing sound from the engine bay or poor engine performance can indicate a vacuum leak.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
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.