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 is not using enough of a special liquid that helps make the exhaust cleaner. It's like not using enough soap when washing your hands.
The P20F4 code indicates that the vehicle's onboard computer has detected that the consumption of the diesel exhaust fluid (DEF), also known as reductant, is lower than expected. This fluid is used to reduce harmful emissions from the exhaust.
The P20F4 code is triggered when the powertrain control module (PCM) detects that the reductant consumption is below the threshold needed for proper operation of the selective catalytic reduction (SCR) system. This can affect the vehicle's ability to reduce NOx emissions.
• Check Engine Light illuminated
• Increased emissions
• Possible reduction in engine performance
• Faulty reductant injector
• Clogged reductant lines
• DEF quality issues
Reductant: A fluid used in diesel engines to reduce harmful emissions.
SCR: Selective Catalytic Reduction, a system used to reduce NOx emissions in diesel engines.
• Check for any additional codes and address them first.
• Inspect the DEF tank for proper fluid level and quality.
• Test the reductant injector and lines for clogs or leaks.
• Replace the reductant injector if faulty.
• Clean or replace clogged reductant lines.
• Refill or replace DEF with the correct fluid.
• OBD-II scanner
• DEF refractometer
• Basic hand tools
$200 - $600
Moderate
• Ford F-250
• Chevrolet Silverado
• Ram 2500
• Regularly check DEF levels.
• Use high-quality DEF fluid.
• Perform scheduled maintenance on the SCR system.
Emissions Control Issue
• Do not ignore the Check Engine Light.
• Use the correct DEF as specified by the manufacturer.
• Schedule a service appointment if unsure.
Emission-related components may be covered under a longer warranty period. Check with the manufacturer.
This code has become more common with the increased use of SCR systems in diesel engines to meet stricter emissions standards.
Moderate – While the vehicle may still operate, emissions are affected and it should be addressed to avoid potential fines or further damage.
Operating a vehicle with excessive emissions may violate local laws and regulations. Ensure repairs are completed to maintain compliance.
• Vehicle at operating temperature
• DEF tank filled with correct fluid
The reductant system is typically located near the exhaust system, with the DEF tank often found near the rear of the vehicle.
Q: Can I drive with a P20F4 code?
A: You can drive, but it's not recommended as it may lead to increased emissions and potential legal issues.
Q: What happens if I ignore this code?
A: Ignoring the code can result in higher emissions, possible fines, and further damage to the emissions system.
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