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 there is a problem with the part of the car that helps keep the special fluid for cleaning exhaust gases warm. It's like when your electric blanket doesn't work because the cord is unplugged.
The P20B5 code indicates an issue with the electrical circuit that controls the heater for the reductant metering unit. This heater is important for ensuring the reductant fluid (like DEF) doesn't freeze in cold temperatures.
The reductant metering unit heater is responsible for maintaining the temperature of the DEF (Diesel Exhaust Fluid) to prevent it from freezing. The P20B5 code is triggered when the Engine Control Module (ECM) detects an open circuit or malfunction in the heater control circuit, which could be due to wiring issues, a faulty heater, or a failed control module.
• Check Engine Light illuminated
• Increased emissions
• Possible reduction in engine performance
• Faulty reductant metering unit heater
• Open or shorted wiring in the heater circuit
• Defective ECM or control module
Reductant: A fluid used in diesel engines to reduce emissions.
DEF: Diesel Exhaust Fluid, a solution used to reduce harmful emissions from diesel engines.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the reductant metering unit heater for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the reductant metering unit heater if faulty.
• Update or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect and maintain the DEF system.
• Ensure wiring and connectors are free from corrosion.
• Keep the vehicle's software updated.
Sensor Issue
• Have the vehicle inspected by a professional if the Check Engine Light comes on.
• Avoid driving in extremely cold conditions until the issue is resolved.
Check with your vehicle manufacturer for warranty coverage on emissions-related components.
This code has become more common with the increased use of DEF systems in diesel vehicles to meet emissions standards.
Moderate – While the vehicle may still be drivable, it can lead to increased emissions and potential engine performance issues.
Driving with this code may lead to failing emissions tests and is not recommended for extended periods.
• Cold weather conditions
• Engine running
The reductant metering unit is typically located near the DEF tank or along the exhaust system.
Q: Can I drive with a P20B5 code?
A: You can drive with this code, but it is not recommended for long periods as it can increase emissions and affect engine performance.
Q: How do I reset the P20B5 code?
A: After repairs, use an OBD-II scanner to clear the code. If the issue is fixed, the code should not return.
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