AutoCodes – Generic – P11BF

P11BF 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 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 907

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

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

What does this mean?

What are the Possible Causes of the DTC P11BF?

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?

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 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 code?

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

Need Help with the Code?

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

Information for Specific Makes

P11BF Buick — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF Cadillac — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF Chevrolet — O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)
P11BF GMC — 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 Code

1. What are some common symptoms of OBDII code P11BF?

- Some common symptoms include poor engine performance, decreased fuel efficiency, and a potential reduction in overall vehicle power.

2. What can cause the OBDII code P11BF to trigger?

- The code P11BF typically triggers due to a malfunction in the O2 reference voltage circuit, specifically indicating low voltage in NOx Sensor 2.

3. How can I diagnose the O2 reference voltage circuit low voltage issue related to code P11BF?

- To diagnose this issue, you may need to use a multimeter to test the voltage in the NOx Sensor 2 circuit and check for any damaged wiring or connections.

4. Can a faulty NOx sensor cause the OBDII code P11BF to appear?

- Yes, a faulty NOx sensor, particularly NOx Sensor 2, can contribute to triggering the P11BF code due to issues with the reference voltage circuit.

5. What are some repair tips for addressing code P11BF?

- Repair tips may include checking and repairing any damaged wiring, replacing the NOx Sensor 2 if necessary, and ensuring all connections related to the O2 reference voltage circuit are secure.

6. Is it safe to continue driving with the OBDII code P11BF present?

- It is not recommended to continue driving with the P11BF code active, as it can lead to further damage to the vehicle and potentially affect emissions output.

7. Can a DIY enthusiast fix the O2 reference voltage circuit low voltage problem related to code P11BF?

- Depending on your skill level and access to tools, you may be able to address the issue yourself by following diagnostic procedures and repair steps outlined in the vehicle's service manual.

8. Are there any recalls related to OBDII code P11BF in certain vehicle models?

- It's advisable to check with the vehicle manufacturer or authorized dealerships to inquire about any recalls or service bulletins related to the P11BF code for specific vehicle models.

9. Will resetting the OBDII system clear the P11BF code permanently?

- Resetting the OBDII system may temporarily clear the code, but if the underlying issue causing the P11BF code is not addressed, it is likely to reappear after driving cycles.

10. How crucial is it to address the OBDII code P11BF promptly?

- It is essential to address the P11BF code promptly to prevent potential damage to the vehicle's emissions system and ensure optimal engine performance and fuel efficiency.