AutoCodes – GMC – P11BF GMC

P11BF GMC Code - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)

Quick Answer

The Nitrogen Oxides (NOx) sensors are part of the selective catalytic reduction system, a device used to reduce NOx emission on diesel engines. Common causes include Faulty Nitrogen Oxides (NOx) Sensor 2, Nitrogen Oxides Sensor 2 harness is open or shorted, Nitrogen Oxides Sensor 2 circuit poor electrical connection. 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: P11BF GMC indicates O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2).
Common causes: Common causes include Faulty Nitrogen Oxides (NOx) Sensor 2, Nitrogen Oxides Sensor 2 harness is open or shorted, Nitrogen Oxides Sensor 2 circuit poor electrical connection.
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.

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Code Popularity 553

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P11BF GMC Description

The Nitrogen Oxides (NOx) sensors are part of the selective catalytic reduction system, a device used to reduce NOx emission on diesel engines. There are two NOx sensors, one placed upstream of selective catalytic reduction, to measure inlet NOx concentration, and one placed downstream. They are connected with the control module via CAN and all the information is exchanged through it. Since it is a smart sensor, all the electrical monitoring is performed inside the sensor and only the results are sent to the Engine Control Module (ECM). Each NOx sensor contains a sensing cell, a pumping cell, and a heater. A sample of exhaust gas passes through a diffusion gap between the sensing cell and the pumping cell. The NOx sensor maintains a constant reference voltage across the sensing cell. An electronic circuit within the sensor controls the pump current through the pumping cell in order to maintain a constant voltage in the sensing cell. The amount of current required to maintain the reference voltage in the sensing cell is proportional to the concentration of NOx in the exhaust. The ECM varies the amount of diesel exhaust fluid (reductant) added by varying the reductant injector duty cycle in response to changes in engine exhaust NOx levels. The smart NOx sensors consist of two components, the NOx module and the NOx sensor element that are serviced as a unit. A circuit or performance condition with a NOx sensor is detected by the NOx sensor module. The smart NOx sensor module communicates the condition to the ECM over the serial data line. The ECM sets a DTC when a serial data message is received from the NOx sensor module. The Diagnostic Trouble Code (DTC) will be set if the ECM software detects a fault in the NOx sensor circuitry or a performance fault in the NOx sensor for greater than 2 s.

OBDII Code P11BF GMC - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com — P11BF GMC Code - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11BF GMC?

Faulty Nitrogen Oxides (NOx) Sensor 2
Nitrogen Oxides Sensor 2 harness is open or shorted
Nitrogen Oxides Sensor 2 circuit poor electrical connection

How to Fix the DTC P11BF GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P11BF GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P11BF GMC code?

Need more information on how to fix the P11BF GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11BF GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P11BF 2014 GMC Sierra — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF 2015 GMC Sierra — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF 2016 GMC Sierra — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF 2017 GMC Sierra — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF 2018 GMC Sierra — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)

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 P11BF GMC Code

1. What does the OBDII code P11BF mean on a GMC vehicle?

P11BF indicates "O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)," meaning the voltage signal from the second NOx sensor's reference circuit is lower than expected.

2. What are the symptoms of a P11BF code on a GMC?

Common symptoms include an illuminated check engine light, decreased fuel efficiency, potential limp mode activation, and higher emissions.

3. What causes the P11BF code to appear on a GMC vehicle?

The P11BF code can be caused by a faulty NOx sensor, wiring issues like corrosion or damage in the sensor circuit, or a malfunctioning engine control module (ECM).

4. Can a bad NOx sensor trigger the P11BF code?

Yes, a defective or failing NOx sensor is one of the primary causes of the P11BF code.

5. How can I diagnose the P11BF code on my GMC?

To diagnose, check the NOx sensor wiring and connectors for damage or corrosion, test the sensor's reference voltage with a multimeter, and use an OBDII scanner to monitor live data.

6. Is the P11BF code related to emissions issues?

Yes, the P11BF code often relates to emissions problems, as the NOx sensor is critical for monitoring and reducing nitrogen oxide levels.

7. How do you fix the P11BF code on a GMC?

Repairs may include replacing the faulty NOx sensor, repairing damaged wiring or connectors, or, in rare cases, reprogramming or replacing the ECM.

8. Can I drive with the P11BF code on my GMC?

Driving with this code is not recommended, as it can lead to increased emissions, reduced fuel efficiency, and potential damage to other components.

9. How much does it cost to fix the P11BF code on a GMC?

The cost varies but typically ranges from $200 to $600, depending on whether the NOx sensor or wiring needs repair or replacement.

10. Is a P11BF code specific to GMC vehicles?

No, it can appear on other vehicles equipped with OBDII systems, but its specifics may vary depending on the manufacturer.

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