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 thinks there's too much fuel in the engine when it's not idling. It's like when you add too much syrup to your pancakes; it's too sweet.
The engine control module (ECM) detects that the fuel mixture is too rich (too much fuel and not enough air) in the 'B' fuel system when the engine is off idle.
The P21F5 code indicates that the ECM has detected a rich condition (excess fuel) in the fuel control system B for bank 1. This can occur when the air-fuel ratio is too low, meaning there is more fuel than necessary for the given amount of air. This condition is detected when the engine is not idling.
• Check Engine Light is on
• Poor fuel economy
• Engine running rough
• Faulty oxygen sensor
• Leaking fuel injector
• Fuel pressure too high
ECM: Engine Control Module
Oxygen Sensor: A device that measures the oxygen level in the exhaust gases
• Use an OBD-II scanner to confirm the code.
• Inspect oxygen sensors and wiring for damage.
• Check fuel pressure and inspect fuel injectors for leaks.
• Replace faulty oxygen sensor.
• Repair or replace leaking fuel injector.
• Adjust or replace fuel pressure regulator.
• OBD-II scanner
• Fuel pressure gauge
• Multimeter
$150 - $500
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regular maintenance and inspection of fuel system.
• Use quality fuel to avoid injector clogging.
• Replace air filters as needed.
Engine Performance
• Avoid driving aggressively to prevent further issues.
• Schedule a service appointment promptly.
Check with your vehicle manufacturer for specific warranty coverage related to emissions and engine components.
This code has been reported in various models with fuel injection systems, often related to sensor or injector issues.
Moderate – Should be addressed soon to prevent potential damage to the catalytic converter.
Driving with a rich fuel mixture can lead to increased emissions and potential damage to the catalytic converter.
• Engine running and warmed up.
• Vehicle not idling.
Oxygen sensors are typically located in the exhaust system, while fuel injectors are located on the engine.
Q: Can I drive with a P21F5 code?
A: It's possible to drive for short distances, but it's recommended to fix the issue soon to avoid further damage.
Q: Will a P21F5 code affect my fuel economy?
A: Yes, a rich fuel mixture can lead to poor fuel economy.
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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.
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.