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 the car's computer has detected that the heater used to warm up a special fluid that helps reduce pollution is using too much electricity.
The P221D code is triggered when the Engine Control Module (ECM) detects that the current draw of the reductant heater B is higher than expected. This could indicate a short circuit or a malfunction in the heater circuit.
The reductant heater is part of the Selective Catalytic Reduction (SCR) system, which reduces NOx emissions in diesel engines. Heater B is one of the components that ensures the reductant (usually urea-based fluid) does not freeze in cold conditions. A current too high error indicates potential electrical issues such as a short circuit or a failing heater element.
• Check Engine Light is on
• Possible increase in emissions
• SCR system may not function properly
• Short circuit in the heater circuit
• Faulty reductant heater B
• Wiring issues or damaged connectors
Reductant: A fluid used in the SCR system to reduce emissions.
SCR: Selective Catalytic Reduction, a system that reduces NOx emissions in diesel engines.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the reductant heater B for proper resistance and functionality.
• Repair or replace damaged wiring or connectors.
• Replace the reductant heater B if it is faulty.
• Clear the code and test drive to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect and maintain the SCR system.
• Ensure reductant fluid is topped up and of good quality.
• Check wiring and connections for wear and tear.
Sensor Issue
• Have a professional inspect the SCR system if unsure.
• Avoid ignoring the Check Engine Light as it can affect emissions.
• Consider preventive maintenance to avoid future issues.
Check with the vehicle manufacturer as emissions-related components may have extended warranties.
This code is more common in colder climates where reductant fluid freezing is a concern.
Moderate – While the vehicle may still be drivable, emissions could be affected, and it should be addressed soon.
Ignoring emissions-related codes can lead to increased pollution and may be illegal in some areas.
• Engine at operating temperature
• Cold ambient conditions to activate the heater
The reductant heater is typically located near the DEF (Diesel Exhaust Fluid) tank or lines.
Q: Can I drive with a P221D code?
A: While the vehicle may still operate, it's not recommended to drive for extended periods as emissions could be affected.
Q: What happens if I ignore this code?
A: Ignoring this code can lead to increased emissions and potential legal issues, as well as further damage to the SCR system.
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