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P11FD 2015 GMC Sierra Code - O2 Low Reference 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: P11FD 2015 GMC Sierra indicates O2 Low Reference 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 144

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 P11FD 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 P11FD 2015 GMC Sierra - O2 Low Reference Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com — P11FD 2015 GMC Sierra Code - O2 Low Reference Circuit Low Voltage (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11FD 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 P11FD 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 P11FD 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 P11FD 2015 GMC Sierra code?

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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 P11FD 2015 GMC Sierra Code

1. What does OBDII code P11FD mean on a 2015 GMC Sierra?

P11FD indicates a problem with the low reference circuit of NOx Sensor 2, specifically low voltage, which affects the sensor's ability to monitor nitrogen oxide levels in the exhaust.

2. What are the common symptoms of code P11FD on a 2015 GMC Sierra?

Symptoms may include a check engine light, reduced fuel efficiency, poor engine performance, or the truck entering reduced power (limp) mode.

3. What causes the P11FD code to appear on a 2015 GMC Sierra?

The code is often caused by a faulty NOx Sensor 2, damaged wiring or connectors in the low reference circuit, or corrosion in the electrical connections.

4. Can I drive my 2015 GMC Sierra with the P11FD code?

While it may be possible to drive temporarily, the truck may experience reduced performance, and prolonged driving with this code could lead to further damage to the emissions system.

5. How do I diagnose the P11FD code on a 2015 GMC Sierra?

Diagnosis involves checking the wiring and connectors for damage or corrosion, testing the voltage in the low reference circuit, and inspecting the NOx Sensor 2 for faults.

6. How do I fix the P11FD code on a 2015 GMC Sierra?

Repairs may include replacing the NOx Sensor 2, repairing or replacing damaged wiring, or cleaning corroded connectors in the low reference circuit.

7. How much does it cost to fix code P11FD on a 2015 GMC Sierra?

Repair costs vary but typically range from $300 to $800 depending on whether the NOx sensor or wiring needs replacement and labor rates in your area.

8. Can a bad NOx sensor cause other problems in my 2015 GMC Sierra?

Yes, a bad NOx sensor can affect emissions performance, trigger limp mode, and cause the vehicle to fail emissions testing.

9. Is a software update needed to fix the P11FD code on a 2015 GMC Sierra?

In some cases, a software update to the engine control module (ECM) may be necessary after replacing the NOx sensor to ensure proper functionality.

10. How do I prevent the P11FD code from reoccurring on my 2015 GMC Sierra?

Regularly inspect and maintain the exhaust and sensor wiring, avoid using contaminated fuel, and address check engine light issues promptly to prevent further damage.