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 electricity supply to a part of the car that helps reduce pollution. It's like when a toy's battery is low and it doesn't work properly.
The P21CA code indicates an issue with the electrical supply to the reductant control module, which manages the diesel exhaust fluid system.
The reductant control module is responsible for controlling the dosing of diesel exhaust fluid (DEF) into the exhaust system to reduce nitrogen oxide emissions. The P21CA code is triggered when the module detects a problem with its power supply circuit, which could be due to low voltage, an open circuit, or a short circuit.
• Check Engine Light is on
• Reduced engine performance
• Increased emissions
• Faulty reductant control module
• Poor electrical connections
• Blown fuse or faulty wiring
Reductant: A substance used to reduce nitrogen oxide emissions in diesel engines.
DEF: Diesel Exhaust Fluid, a liquid used in diesel engines to reduce emissions.
• Check for any blown fuses related to the reductant control module.
• Inspect wiring and connectors for damage or corrosion.
• Test the voltage supply to the reductant control module.
• Replace blown fuses.
• Repair or replace damaged wiring or connectors.
• Replace the reductant control module if faulty.
• Multimeter
• OBD-II scanner
• Basic hand tools
$150 - $500
Moderate
• Ford F-250
• Chevrolet Silverado
• Ram 2500
• Regularly inspect and maintain electrical connections.
• Ensure the battery and charging system are in good condition.
• Keep the DEF system clean and properly filled.
Electrical Circuit Issue
• Avoid driving long distances until the issue is resolved.
• Consult with a professional mechanic for accurate diagnosis.
Check with the 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 – Should be addressed soon to avoid increased emissions and potential engine performance issues.
Operating a vehicle with this code may result in higher emissions, which could be against local environmental regulations.
• Engine running
• Electrical system fully operational
The reductant control module is typically located near the DEF tank or within the engine compartment.
Q: Can I drive with a P21CA code?
A: It's possible to drive short distances, but it's not recommended as it may increase emissions and affect engine performance.
Q: What happens if I ignore the P21CA code?
A: Ignoring the code can lead to increased emissions, possible damage to the DEF system, and reduced engine performance.
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