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P11FE 2018 GMC Sierra Code - O2 Low Reference Circuit High 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
P11FE 2018 GMC Sierra indicates O2 Low Reference Circuit High 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 174
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Mar 24, 2024
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Code P11FE 2018 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 P11FE 2018 GMC Sierra - O2 Low Reference Circuit High Voltage (NOx Sensor 2) - AutoCodes.com
P11FE 2018 GMC Sierra Code - O2 Low Reference Circuit High Voltage (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11FE 2018 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 P11FE 2018 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 P11FE 2018 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 P11FE 2018 GMC Sierra code?

Need more information on how to fix the P11FE 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11FE 2018 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 P11FE 2018 GMC Sierra Code

1. What does the OBDII code P11FE mean on a 2018 GMC Sierra?

The P11FE code indicates an issue with the O2 low reference circuit, specifically high voltage detected in NOx Sensor 2, which monitors nitrogen oxide emissions.

2. What are the common symptoms of the P11FE code on a 2018 GMC Sierra?

Symptoms may include the check engine light turning on, reduced engine performance, poor fuel efficiency, or the vehicle entering limp mode.

3. What causes the P11FE code on a 2018 GMC Sierra?

Common causes include a faulty NOx sensor 2, damaged wiring or connectors in the O2 reference circuit, exhaust leaks, or a malfunctioning Engine Control Module (ECM).

4. Can I drive my 2018 GMC Sierra with the P11FE code?

While the vehicle may still be drivable, it’s not recommended due to potential engine performance issues and increased emissions, which could lead to further damage.

5. How is the P11FE code diagnosed?

A technician will use a scan tool to retrieve the code, inspect the NOx sensor and wiring for damage, and test the circuit voltages to identify the source of the issue.

6. How do I fix the P11FE code on my 2018 GMC Sierra?

Repairs may include replacing the faulty NOx sensor 2, repairing damaged wiring or connectors, addressing any exhaust leaks, or reprogramming or replacing the ECM if necessary.

7. What is the role of NOx Sensor 2 in a 2018 GMC Sierra?

NOx Sensor 2 measures nitrogen oxide levels in the exhaust system to ensure the vehicle meets emissions standards and operates efficiently.

8. How much does it cost to repair the P11FE code on a 2018 GMC Sierra?

Repair costs can vary but typically range from $300 to $600 for replacing a defective NOx sensor, with additional costs if wiring or ECM repairs are needed.

9. Can a dirty exhaust system cause the P11FE code?

Yes, a clogged or leaking exhaust system can impact NOx sensor readings and trigger the P11FE code.

10. Will clearing the P11FE code solve the problem?

Clearing the code may turn off the check engine light temporarily, but the issue will likely reoccur unless the underlying problem is fixed.

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