Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a part in your car that helps control the temperature of a special fluid used to reduce pollution, and it's not working right because it's stuck open.
The P20B2 code indicates an issue with the control valve that manages the flow of coolant to the reductant heater. This valve is not performing as expected, likely because it is stuck in the open position.
The reductant heater coolant control valve is responsible for regulating the flow of coolant to the reductant heater system. When this valve is stuck open, it can cause improper heating of the reductant fluid, which is crucial for the vehicle's emissions system to function correctly. This can lead to increased emissions and potential damage to the emissions system.
• Check Engine Light illuminated
• Increased vehicle emissions
• Possible reduction in fuel efficiency
• Emissions test failure
• Faulty reductant heater coolant control valve
• Electrical issues in the valve circuit
• Blockage or debris in the valve
• Faulty wiring or connectors
Reductant: A fluid used in diesel engines to reduce emissions.
Coolant: A fluid that helps regulate engine temperature.
• Use an OBD-II scanner to confirm the P20B2 code.
• Inspect the reductant heater coolant control valve for physical damage or blockage.
• Check the electrical connections and wiring to the valve.
• Test the valve operation using a multimeter or diagnostic tool.
• Replace the reductant heater coolant control valve if faulty.
• Repair or replace damaged wiring or connectors.
• Clear any blockages or debris from the valve.
• Reset the OBD-II codes and test the vehicle.
• OBD-II scanner
• Multimeter
• Wrench set
• Screwdriver set
$150 - $400
Moderate
• Ford F-250
• Chevrolet Silverado
• RAM 2500
• Regular maintenance of the emissions system
• Periodic inspection of the reductant system components
• Use high-quality reductant fluid
Emissions System Issue
• Address the issue promptly to avoid increased emissions.
• Consult with a professional mechanic for accurate diagnosis.
• Ensure regular vehicle maintenance to prevent such issues.
Check with your vehicle manufacturer as emissions-related components may be covered under warranty.
This code has become more common with the increased use of selective catalytic reduction (SCR) systems in diesel vehicles.
Moderate – It should be addressed soon to prevent emissions issues and potential damage to the emissions system.
Ignoring emissions-related issues can result in failing emissions tests and may be illegal in some regions.
• Engine at operating temperature
• Vehicle in a safe, stationary position
The reductant heater coolant control valve is typically located near the reductant tank or along the coolant line leading to the heater.
Q: Can I drive with a P20B2 code?
A: While the vehicle may still be drivable, it's best to address the issue soon to avoid emissions problems.
Q: How do I reset the Check Engine Light after fixing the issue?
A: Use an OBD-II scanner to clear the code after repairs are completed.
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.