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 problem with the part of the car that helps keep a special fluid warm. This fluid helps reduce pollution from the car's exhaust.
The P20B9 code indicates that the Engine Control Module (ECM) has detected an issue with the control circuit of the reductant heater A, which is responsible for heating the diesel exhaust fluid (DEF) to ensure it functions properly.
The reductant heater A is part of the Selective Catalytic Reduction (SCR) system in diesel engines. It heats the DEF to prevent it from freezing and ensures proper dosing into the exhaust stream. An open or faulty control circuit can prevent the heater from functioning, potentially affecting emissions control.
• Check Engine Light illuminated
• Reduced engine performance
• Increased emissions
• Poor fuel economy
• Faulty reductant heater A
• Open or shorted heater circuit
• Faulty wiring or connectors
• Blown fuse
• Faulty ECM
Reductant: A substance used to reduce emissions in the exhaust system.
DEF: Diesel Exhaust Fluid, a solution used in diesel engines to reduce harmful emissions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Check the fuse related to the reductant heater.
• Test the heater circuit for continuity.
• Inspect the ECM for faults.
• Replace the faulty reductant heater A.
• Repair or replace damaged wiring or connectors.
• Replace the blown fuse.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 to $500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect the SCR system components.
• Ensure proper maintenance of the vehicle's electrical system.
• Use high-quality DEF fluid.
Sensor Issue
• Do not ignore the Check Engine Light.
• Seek professional diagnosis if unsure.
• Regular maintenance can prevent such issues.
Check with the vehicle manufacturer for specific warranty coverage related to emissions components.
This code has been more prevalent in vehicles with diesel engines equipped with SCR systems, especially in colder climates where DEF freezing is a concern.
Moderate – While the vehicle may still be drivable, emissions and performance can be affected.
Operating a vehicle with increased emissions may violate environmental regulations.
• Engine at operating temperature
• Cold ambient temperatures
The reductant heater is typically located near the DEF tank or within the DEF dosing unit.
Q: Can I drive with a P20B9 code?
A: You can drive, but it's best to address the issue soon to avoid increased emissions and potential engine performance issues.
Q: What happens if I ignore this code?
A: Ignoring the code can lead to increased emissions, reduced fuel efficiency, and potential damage to the SCR system.
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