Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means something is blocking the special liquid that helps clean the car's exhaust, so it can't flow properly.
The reductant system in vehicles, often using Diesel Exhaust Fluid (DEF), is responsible for reducing emissions. A blocked flow indicates that the fluid is not moving as it should, possibly due to a clog or malfunction.
The P2D20 code is triggered when the Engine Control Module (ECM) detects a blockage in the reductant system flow. This system is crucial for the Selective Catalytic Reduction (SCR) process, which reduces nitrogen oxide emissions in diesel engines. A blockage could be due to crystallization, a clogged injector, or a faulty pump.
• Check engine light on
• Reduced engine performance
• Increased emissions
• Clogged reductant injector
• Crystallization of DEF in lines
• Faulty reductant pump
Reductant: A substance used to reduce emissions in a vehicle's exhaust system.
SCR: Selective Catalytic Reduction, a system that reduces nitrogen oxide emissions in diesel engines.
• Check for any stored trouble codes.
• Inspect the reductant system for blockages.
• Test the reductant pump and injector functionality.
• Clean or replace the reductant injector.
• Flush the reductant lines to remove crystallization.
• Replace the reductant pump if faulty.
• OBD-II scanner
• Wrench set
• DEF line cleaning kit
$200 - $600
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly check and refill DEF levels.
• Use high-quality DEF to prevent crystallization.
• Perform regular maintenance on the SCR system.
Emission Control Issue
• Do not ignore the check engine light.
• Have the system inspected by a professional if unsure.
• Avoid driving long distances with this issue to prevent further damage.
Check your vehicle's warranty for coverage on emission-related components.
This code has become more common with the increased use of SCR systems in diesel engines to meet emission standards.
Moderate – Addressing this issue promptly can prevent increased emissions and potential engine damage.
Operating a vehicle with a malfunctioning emission system may violate environmental regulations and lead to fines.
• Engine at operating temperature
• Vehicle in a safe environment for testing
The reductant system components are typically located near the exhaust system, including the DEF tank and injector.
Q: Can I drive with a P2D20 code?
A: It's not recommended to drive for long periods with this code, as it can lead to increased emissions and potential engine issues.
Q: What is DEF?
A: Diesel Exhaust Fluid (DEF) is a liquid used in the SCR system to reduce nitrogen oxide emissions from diesel engines.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.