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's a problem with the part of the car that helps keep a special fluid warm. This fluid helps clean the car's exhaust so it doesn't pollute too much. If the fluid isn't warm enough, it can't do its job right.
The P20B7 code indicates that the control circuit for the heater in the reductant metering unit is reading a low voltage. This heater is necessary to ensure the reductant fluid (such as DEF in diesel engines) remains at the optimal temperature for effective emission control.
The reductant metering unit heater is responsible for maintaining the temperature of the diesel exhaust fluid (DEF) or another reductant to prevent it from freezing in cold conditions. A low circuit reading suggests that there is an issue with the electrical circuit, such as a poor connection, damaged wiring, or a faulty heater.
• Check Engine Light illuminated
• Increased exhaust emissions
• Poor engine performance
• Faulty reductant metering unit heater
• Damaged or corroded wiring or connectors
• Faulty control module or relay
Reductant: A substance used to reduce emissions in the exhaust system, such as DEF.
DEF: Diesel Exhaust Fluid, a liquid used in diesel engines to reduce emissions.
• 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.
• Replace the control module or relay if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect and maintain the exhaust system.
• Ensure proper DEF fluid levels and quality.
• Keep electrical connections clean and secure.
Sensor Issue
• Do not ignore the Check Engine Light.
• Schedule a diagnostic check with a professional mechanic.
• Avoid driving in extremely cold conditions until the issue is resolved.
Check with your vehicle manufacturer; emissions-related components may be covered under warranty.
This code has become more common with the increased use of DEF systems in diesel engines to meet stricter emission standards.
Moderate – While the vehicle may still be drivable, emissions and performance can be affected.
Driving with an emissions-related fault can lead to increased pollution and may not comply with local emissions laws.
• Engine at operating temperature
• Cold ambient conditions to test heater function
The reductant metering unit is typically located near the DEF tank or along the exhaust system.
Q: Can I drive with a P20B7 code?
A: While you may be able to drive, it's best to fix the issue to avoid increased emissions and potential engine performance problems.
Q: What happens if I ignore this code?
A: Ignoring this code can lead to higher emissions, potential engine performance issues, and may result in failing an emissions test.
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