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 the system that cleans up some of the bad stuff from the engine isn't working well enough on one side of the engine.
The Selective Catalytic Reduction (SCR) system is not reducing NOx emissions efficiently before the catalyst on Bank 2.
The P20F3 code is triggered when the Engine Control Module (ECM) detects that the efficiency of the Selective Catalytic Reduction (SCR) system is below the expected threshold for Bank 2. This means the system is not effectively reducing nitrogen oxides (NOx) emissions before they reach the catalyst.
• Check Engine Light is on
• Reduced fuel efficiency
• Possible increase in exhaust smoke
• Faulty SCR catalyst
• Defective NOx sensor
• Incorrect or contaminated Diesel Exhaust Fluid (DEF)
SCR: Selective Catalytic Reduction
NOx: Nitrogen Oxides
DEF: Diesel Exhaust Fluid
• Use an OBD-II scanner to confirm the code.
• Inspect the SCR system and NOx sensors for damage or faults.
• Check the quality and level of Diesel Exhaust Fluid (DEF).
• Replace the SCR catalyst if faulty.
• Replace or repair the NOx sensor.
• Refill or replace the Diesel Exhaust Fluid (DEF) if contaminated.
• OBD-II scanner
• Wrench set
• Multimeter
$500 - $1500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly check and refill DEF.
• Perform routine maintenance on the SCR system.
• Use high-quality DEF to avoid contamination.
Emission Control System Issue
• Avoid driving long distances until the issue is fixed.
• Ensure regular maintenance is performed on the vehicle.
SCR components may be covered under emissions warranty; check with the manufacturer.
This code has become more common as emissions standards have tightened, requiring more complex SCR systems.
Moderate – Should be addressed soon to avoid increased emissions and potential engine damage.
Operating a vehicle with this code may result in failing emissions tests and is not environmentally friendly.
• Engine at operating temperature
• Vehicle driven under normal conditions
The SCR system is located in the exhaust system, typically under the vehicle, near the catalytic converter on Bank 2.
Q: What is SCR?
A: SCR stands for Selective Catalytic Reduction, a system that reduces NOx emissions in diesel engines.
Q: Can I drive with a P20F3 code?
A: While the vehicle may still drive, it's not recommended to ignore this code as it affects emissions and could lead to further issues.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
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.