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P11C0 2018 GMC Sierra Code - O2 Reference Voltage 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
P11C0 2018 GMC Sierra indicates O2 Reference Voltage 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 275
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 P11C0 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 P11C0 2018 GMC Sierra - O2 Reference Voltage Circuit High Voltage (NOx Sensor 2) - AutoCodes.com
P11C0 2018 GMC Sierra Code - O2 Reference Voltage Circuit High Voltage (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11C0 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 P11C0 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 P11C0 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 P11C0 2018 GMC Sierra code?

Need more information on how to fix the P11C0 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11C0 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 P11C0 2018 GMC Sierra Code

1. What does the OBDII code P11C0 mean on a 2018 GMC Sierra?

The P11C0 code indicates an "O2 Reference Voltage Circuit High Voltage" issue with NOx Sensor 2, which monitors nitrogen oxide emissions in the exhaust system.

2. What are common symptoms of the P11C0 code in a 2018 GMC Sierra?

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

3. What causes the P11C0 code to appear on a 2018 GMC Sierra?

Common causes include a faulty NOx sensor, damaged wiring or connectors in the O2 reference voltage circuit, or issues with the ECM (Engine Control Module).

4. How can I diagnose the P11C0 code on my GMC Sierra?

Start by using an OBDII scanner to confirm the code, then inspect the NOx Sensor 2, its wiring, and connectors for damage or corrosion. Check the O2 reference voltage readings with a multimeter.

5. Can a faulty NOx sensor cause the P11C0 code?

Yes, a malfunctioning NOx sensor can cause the O2 reference voltage to be out of range, triggering the P11C0 code.

6. Is it safe to drive my 2018 GMC Sierra with the P11C0 code?

Driving with this code may cause poor performance and increased emissions. If the vehicle enters limp mode, it should not be driven for long distances. Address the issue promptly.

7. How do I fix the P11C0 code on my GMC Sierra?

Repairs may involve replacing the faulty NOx sensor, repairing or replacing damaged wiring, or reprogramming the ECM if necessary.

8. Can a software update fix the P11C0 code?

In some cases, a software update for the ECM may resolve the issue if it is related to incorrect voltage thresholds being set.

9. How much does it cost to fix the P11C0 code on a 2018 GMC Sierra?

Repair costs vary but typically range from $200 to $600, depending on whether you're replacing the NOx sensor or addressing wiring issues.

10. How can I prevent the P11C0 code from reappearing?

Regular maintenance, inspecting the exhaust system components, and addressing wiring issues promptly can help prevent the P11C0 code from returning.

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