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P20BF 2018 GMC Sierra Code - Reductant Heater 2 Control Circuit Low Voltage

Quick Answer

The P20BF diagnostic trouble code (DTC) for a 2018 GMC Sierra specifically refers to the Reductant Heater 2 Control Circuit Low Voltage. Common causes include Faulty Reductant Heater: The Reductant Heater itself may be malfunctioning, leading to low voltage in the control circuit, Wiring Issues: Corrosion, damage, or loose connections in the wiring harness connected to the Reductant Heater can cause low voltage, PCM Malfunction: A problem with the Powertrain Control Module (PCM) can also trigger the P20BF code. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P20BF 2018 GMC Sierra indicates Reductant Heater 2 Control Circuit Low Voltage.
Common causes
Common causes include Faulty Reductant Heater: The Reductant Heater itself may be malfunctioning, leading to low voltage in the control circuit, Wiring Issues: Corrosion, damage, or loose connections in the wiring harness connected to the Reductant Heater can cause low voltage, PCM Malfunction: A problem with the Powertrain Control Module (PCM) can also trigger the P20BF code.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 16, 2024
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Code P20BF 2018 GMC Sierra Description

The P20BF diagnostic trouble code (DTC) for a 2018 GMC Sierra specifically refers to the Reductant Heater 2 Control Circuit Low Voltage. In modern diesel vehicles, Selective Catalytic Reduction (SCR) systems are used to reduce harmful emissions by injecting a urea-based solution (diesel exhaust fluid or DEF) into the exhaust stream. The Reductant Heater is responsible for maintaining the DEF at the optimal temperature to ensure efficient conversion of harmful nitrogen oxides (NOx) into harmless nitrogen and water vapor.

OBDII Code P20BF 2018 GMC Sierra - Reductant Heater 2 Control Circuit Low Voltage
P20BF 2018 GMC Sierra Code - Reductant Heater 2 Control Circuit Low Voltage

Common Causes of P20BF 2018 GMC Sierra

  1. Faulty Reductant Heater: The Reductant Heater itself may be malfunctioning, leading to low voltage in the control circuit.
  2. Wiring Issues: Corrosion, damage, or loose connections in the wiring harness connected to the Reductant Heater can cause low voltage.
  3. PCM Malfunction: A problem with the Powertrain Control Module (PCM) can also trigger the P20BF code.
  4. DEF Quality: Contaminated or low-quality DEF can impact the efficiency of the Reductant Heater and trigger the code.
  5. Environmental Factors: Extreme temperatures or exposure to moisture can also affect the Reductant Heater's performance.

Symptoms of P20BF 2018 GMC Sierra

  1. Check Engine Light: The most common symptom associated with the P20BF code is the illumination of the Check Engine Light on the vehicle's dashboard.
  2. Reduced DEF Efficiency: Drivers may notice a decrease in DEF consumption or a warning message indicating DEF system issues.
  3. Poor Performance: The vehicle may experience reduced power, hesitation, or rough idling due to inefficient emission control.
  4. Failed Emissions Test: If the issue is not resolved, the vehicle may fail emissions testing due to increased NOx emissions.

How to Fix P20BF 2018 GMC Sierra

  1. Diagnose the Issue: Use a diagnostic scanner to retrieve the specific DTC and perform a thorough inspection of the Reductant Heater system.
  2. Check Wiring and Connections: Inspect the wiring harness for any damage, corrosion, or loose connections and repair or replace as needed.
  3. Test Reductant Heater: Verify the functionality of the Reductant Heater by testing its resistance and voltage output.
  4. Replace Reductant Heater: If the heater is found to be faulty, replace it with a new unit following manufacturer guidelines.
  5. Clear Codes and Test Drive: After completing the repair, clear the DTCs from the PCM memory and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P20BF 2018 GMC Sierra

The typical repair costs for addressing a P20BF code on a 2018 GMC Sierra can vary depending on the specific cause of the issue. In general, replacing a faulty Reductant Heater can cost between $200 and $500, including parts and labor. However, additional costs may apply if wiring repairs or PCM reprogramming are necessary. It's important to note that diagnosis time and labor rates at auto repair shops can vary, with hourly rates typically ranging from $80 to $150. Factors such as location, vehicle make and model, and engine type can also influence the final repair costs. Therefore, it's recommended to consult with a trusted mechanic or dealership for a more accurate estimate based on the specific circumstances.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P20BF 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code P20BF in a 2018 GMC Sierra related to Reductant Heater 2 Control Circuit Low Voltage?

The common symptoms include the check engine light illuminating, reduced engine power, and potential issues with the vehicle's emissions system.

2. What are the possible causes of OBDII code P20BF on a 2018 GMC Sierra indicating Reductant Heater 2 Control Circuit Low Voltage?

Possible causes include a faulty reductant heater, damaged wiring or connectors in the reductant heater circuit, a malfunctioning temperature sensor, or issues with the powertrain control module (PCM).

3. How can I diagnose the OBDII code P20BF on my 2018 GMC Sierra?

Diagnosis involves using an OBDII scanner to read the code, checking the reductant heater system for any visible damage, inspecting wiring and connectors for corrosion or breaks, and testing the temperature sensor and related components.

4. Can I continue driving my 2018 GMC Sierra with OBDII code P20BF indicating Reductant Heater 2 Control Circuit Low Voltage?

It is not recommended to continue driving the vehicle with this code, as it can lead to reduced engine performance and potential damage to the emissions system. It is best to address the issue promptly.

5. How can I repair OBDII code P20BF on my 2018 GMC Sierra related to Reductant Heater 2 Control Circuit Low Voltage?

Repair options include replacing the faulty reductant heater, repairing or replacing damaged wiring and connectors, checking and replacing the temperature sensor if needed, and resetting the code using an OBDII scanner after repairs are completed.

6. Are there any specific maintenance tips to prevent OBDII code P20BF on a 2018 GMC Sierra?

Regularly inspecting the emissions system components, ensuring proper maintenance of the reductant heater system, and addressing any warning signs promptly can help prevent issues leading to this fault code.

7. Can weather conditions affect OBDII code P20BF in a 2018 GMC Sierra related to Reductant Heater 2 Control Circuit Low Voltage?

Extreme weather conditions can potentially impact the performance of the reductant heater system, leading to issues that trigger this fault code. It is essential to keep the vehicle well maintained in all weather conditions.

8. Is OBDII code P20BF in a 2018 GMC Sierra covered under any warranty or recall?

It is advisable to check with a GMC dealership or the manufacturer to see if the issue related to this fault code is covered under any existing warranty or recall for the specific model year and vehicle.

9. Can I clear the OBDII code P20BF on my 2018 GMC Sierra without fixing the underlying issue?

While you can clear the code using an OBDII scanner, it is not recommended to do so without addressing the root cause. Ignoring the underlying problem can lead to further issues and potential damage to the vehicle in the long run.

10. How long does it typically take to repair OBDII code P20BF on a 2018 GMC Sierra?

The repair time can vary depending on the exact cause of the fault code and the complexity of the repair. It is best to consult with a mechanic or dealership for a more accurate estimate based on the specific diagnosis of the issue.

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