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 thinks the sensor that checks how much special fluid (used to clean the exhaust) is in the tank is not working right. It's like when your video game controller says the battery is full, but it's actually not.
The P21B0 code is triggered when the vehicle's Engine Control Module (ECM) detects a high voltage signal from the reductant level sensor circuit C, indicating a potential issue with the sensor or its circuit.
The reductant level sensor is part of the vehicle's Selective Catalytic Reduction (SCR) system, which helps reduce emissions. The sensor monitors the level of Diesel Exhaust Fluid (DEF) in the tank. A 'circuit high' condition suggests that the voltage in the sensor's circuit is higher than expected, which could be due to a faulty sensor, wiring issues, or a problem with the ECM.
• Check Engine Light is on
• Possible reduction in engine performance
• SCR system warning light may be illuminated
• Faulty reductant level sensor
• Wiring issues such as open or short circuits
• Faulty Engine Control Module (ECM)
Reductant: A substance used to reduce emissions, typically Diesel Exhaust Fluid (DEF) in diesel engines.
SCR: Selective Catalytic Reduction, a system used to reduce vehicle emissions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors related to the reductant level sensor.
• Test the reductant level sensor for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the reductant level sensor if faulty.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Ford F-250
• Chevrolet Silverado
• Dodge Ram 2500
• Regularly check and maintain DEF levels.
• Inspect wiring and connectors for damage.
• Ensure proper maintenance of the SCR system.
Sensor Issue
• Do not ignore the warning light; have the vehicle inspected.
• Regularly maintain the DEF system to prevent issues.
• Consult a professional mechanic for accurate diagnosis.
Check with the vehicle manufacturer for specific warranty coverage related to emissions control systems.
The P21B0 code has been associated with vehicles equipped with SCR systems since the implementation of stricter emissions standards.
Moderate – Addressing this issue promptly can prevent further emissions-related problems.
Ignoring emissions-related codes can lead to increased pollution and may not comply with local emissions regulations.
• Engine running
• Vehicle at operating temperature
The reductant level sensor is typically located in or near the Diesel Exhaust Fluid (DEF) tank.
Q: Can I drive with a P21B0 code?
A: While the vehicle may still be drivable, it's important to address the issue to avoid potential emissions system damage.
Q: What is Diesel Exhaust Fluid (DEF)?
A: DEF is a liquid used in diesel engines to reduce harmful emissions by breaking down nitrogen oxides in the exhaust.
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