AutoCodes – GMC – P11C8 2018 GMC Sierra

P11C8 2018 GMC Sierra Code - NOx Sensor 2 Heater Ground Circuit High

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: P11C8 2018 GMC Sierra indicates NOx Sensor 2 Heater Ground Circuit High.
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 159

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 P11C8 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 P11C8 2018 GMC Sierra - NOx Sensor 2 Heater Ground Circuit High - AutoCodes.com — P11C8 2018 GMC Sierra Code - NOx Sensor 2 Heater Ground Circuit High

What does this mean?

What are the Possible Causes of the DTC P11C8 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 P11C8 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 P11C8 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 P11C8 2018 GMC Sierra code?

Need more information on how to fix the P11C8 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11C8 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 P11C8 2018 GMC Sierra Code

1. What does the OBDII code P11C8 mean on a 2018 GMC Sierra?

The P11C8 code indicates a problem with the NOx Sensor 2 Heater Ground Circuit being too high, meaning there is an electrical issue affecting the heater circuit for the second NOx sensor.

2. What are the common symptoms of the P11C8 code?

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

3. What causes the P11C8 code?

Common causes include a damaged NOx sensor, a faulty heater circuit, issues with the ground wiring or connections, or a malfunctioning Engine Control Module (ECM).

4. Can I drive my 2018 GMC Sierra with the P11C8 code active?

While the vehicle may still be drivable, itâ€™s not recommended to ignore the issue as it can lead to reduced performance, increased emissions, and potential damage to other components.

5. How do I troubleshoot the P11C8 code?

Start by inspecting the wiring and connections to the NOx Sensor 2 for damage or corrosion. Check the resistance of the heater circuit and verify proper grounding. Replace the sensor if necessary.

6. How much does it cost to fix the P11C8 code?

The cost to repair can vary but typically ranges from $300 to $600 if the NOx sensor needs replacement. Wiring repairs may cost less depending on the extent of the damage.

7. Can a faulty NOx sensor cause other problems in my truck?

Yes, a faulty NOx sensor can lead to increased emissions, reduced fuel efficiency, and improper operation of the vehicle's exhaust after-treatment system.

8. Is the P11C8 code covered under warranty for a 2018 GMC Sierra?

It may be covered under the emissions warranty, depending on your vehicleâ€™s mileage and warranty terms. Check with your dealer for confirmation.

9. What tools are needed to diagnose the P11C8 code?

Youâ€™ll need an OBDII scanner, a multimeter for checking resistance, and possibly a wiring diagram to trace circuits for troubleshooting.

10. How can I prevent the P11C8 code from occurring again?

Ensure regular maintenance of the vehicleâ€™s exhaust system, avoid using low-quality fuel, and inspect wiring and connectors periodically for wear or corrosion.