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P1193 2018 GMC Sierra Code - O2 Low Reference Circuit Low Voltage (NOx Sensor 1)

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, Nitrogen Oxides Sensor harness is open or shorted, Nitrogen Oxides Sensor 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
P1193 2018 GMC Sierra indicates O2 Low Reference Circuit Low Voltage (NOx Sensor 1).
Common causes
Common causes include Faulty Nitrogen Oxides (NOx) Sensor, Nitrogen Oxides Sensor harness is open or shorted, Nitrogen Oxides Sensor 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 199
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 P1193 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 P1193 2018 GMC Sierra - O2 Low Reference Circuit Low Voltage (NOx Sensor 1) - AutoCodes.com
P1193 2018 GMC Sierra Code - O2 Low Reference Circuit Low Voltage (NOx Sensor 1)
What does this mean?

What are the Possible Causes of the DTC P1193 2018 GMC Sierra?

  • Faulty Nitrogen Oxides (NOx) Sensor
  • Nitrogen Oxides Sensor harness is open or shorted
  • Nitrogen Oxides Sensor circuit poor electrical connection

How to Fix the DTC P1193 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 P1193 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 P1193 2018 GMC Sierra code?

Need more information on how to fix the P1193 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the 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 P1193 2018 GMC Sierra Code

1. What does the OBDII code P1193 mean on a 2018 GMC Sierra?

The P1193 code indicates "O2 Low Reference Circuit Low Voltage (NOx Sensor 1)," meaning the NOx sensor is detecting an abnormally low voltage in the oxygen reference circuit.

2. What are the common symptoms of a P1193 code on a 2018 GMC Sierra?

Symptoms include an illuminated check engine light, reduced engine performance, poor fuel economy, and possible diesel exhaust fluid (DEF) system warnings.

3. What causes the P1193 code to appear on a 2018 GMC Sierra?

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

4. Can a faulty NOx sensor cause a P1193 code?

Yes, a faulty NOx sensor is a primary cause of the P1193 code, as it may fail to send proper voltage signals to the ECM.

5. How do I diagnose a P1193 code on my 2018 GMC Sierra?

Diagnose the issue by scanning for additional codes, inspecting the NOx sensor wiring and connectors, and testing the sensor's voltage output with a multimeter.

6. Can I drive my 2018 GMC Sierra with a P1193 code?

You may be able to drive with a P1193 code, but it’s not recommended as it could lead to reduced engine performance and potential damage to the emissions system.

7. How do I fix the P1193 code on a 2018 GMC Sierra?

Repairs may include replacing the NOx sensor, repairing or replacing damaged wiring, cleaning corroded connectors, or reprogramming the ECM if necessary.

8. How much does it cost to fix a P1193 code on a 2018 GMC Sierra?

The cost depends on the issue, but replacing the NOx sensor typically costs $300-$600, while wiring repairs can vary from $50 to $200.

9. Can a software update resolve the P1193 code on a 2018 GMC Sierra?

In some cases, a software update for the ECM might resolve the issue, but this is less common than physical repairs like replacing the NOx sensor.

10. What happens if I ignore the P1193 code on my 2018 GMC Sierra?

Ignoring the P1193 code can lead to worsening engine performance, higher emissions, and potential damage to other emissions system components.

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