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AutoCodes – GMC – P11FC 2015 GMC Sierra

P11FC 2015 GMC Sierra Code - O2 Low Reference Circuit (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
P11FC 2015 GMC Sierra indicates O2 Low Reference Circuit (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 148
How popular is this code, among other codes? Low
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Table of contents Created and updated by William Orellana on Mar 24, 2024
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Code P11FC 2015 GMC Sierra 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 P11FC 2015 GMC Sierra - O2 Low Reference Circuit (NOx Sensor 2) - AutoCodes.com
P11FC 2015 GMC Sierra Code - O2 Low Reference Circuit (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11FC 2015 GMC Sierra?

  • 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 P11FC 2015 GMC Sierra?

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 P11FC 2015 GMC Sierra 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 P11FC 2015 GMC Sierra code?

Need more information on how to fix the P11FC 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11FC 2015 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 P11FC 2015 GMC Sierra Code

1. What does the OBDII code P11FC mean on a 2015 GMC Sierra?

P11FC indicates an issue with the O2 low reference circuit for NOx Sensor 2, which is part of the emissions system.

2. What are the common symptoms of code P11FC on a 2015 GMC Sierra?

Symptoms may include the check engine light turning on, reduced fuel efficiency, poor engine performance, and possible emissions test failure.

3. What causes the P11FC code to appear on a 2015 GMC Sierra?

Common causes include a faulty NOx sensor, damaged wiring or connectors, corrosion in the O2 reference circuit, or issues with the engine control module (ECM).

4. Can I drive my 2015 GMC Sierra with the P11FC code?

While the truck may still be drivable, ignoring the issue could lead to increased emissions, reduced performance, and potential damage to the emissions system.

5. How do I fix the P11FC code on my 2015 GMC Sierra?

Inspect and repair any damaged wiring or connectors to the NOx sensor, clean or replace the NOx sensor if necessary, and clear the code with a scan tool.

6. How much does it cost to repair the P11FC code on a 2015 GMC Sierra?

Repair costs vary but typically range from $200 to $600, depending on whether the NOx sensor or wiring needs replacement.

7. What tools are required to diagnose the P11FC code on a 2015 GMC Sierra?

You’ll need an OBDII scan tool, a multimeter to test wiring, and potentially a NOx sensor socket for removal.

8. Where is NOx Sensor 2 located on a 2015 GMC Sierra?

NOx Sensor 2 is usually located downstream in the exhaust system, after the catalytic converter.

9. Can a dirty or clogged diesel particulate filter (DPF) cause the P11FC code?

While not a direct cause, a clogged DPF can increase exhaust backpressure, potentially affecting the performance of the NOx sensor.

10. Will clearing the P11FC code with a scan tool fix the issue permanently?

No, clearing the code without addressing the underlying problem will likely result in the code reappearing. Proper diagnosis and repair are required.

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