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P1194 2017 GMC Sierra Code - O2 Low Reference Circuit High 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
P1194 2017 GMC Sierra indicates O2 Low Reference Circuit High 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 166
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 P1194 2017 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 P1194 2017 GMC Sierra - O2 Low Reference Circuit High Voltage (NOx Sensor 1) - AutoCodes.com
P1194 2017 GMC Sierra Code - O2 Low Reference Circuit High Voltage (NOx Sensor 1)
What does this mean?

What are the Possible Causes of the DTC P1194 2017 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 P1194 2017 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 P1194 2017 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 P1194 2017 GMC Sierra code?

Need more information on how to fix the P1194 2017 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1194 2017 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 P1194 2017 GMC Sierra Code

1. What does the OBDII code P1194 mean on a 2017 GMC Sierra?

P1194 refers to "O2 Low Reference Circuit High Voltage" and is associated with NOx Sensor 1, indicating an issue with high voltage in the low reference circuit of the sensor.

2. What are the common symptoms of code P1194 on a 2017 GMC Sierra?

Common symptoms include an illuminated check engine light, reduced fuel efficiency, poor engine performance, and possible increased emissions.

3. What causes P1194 on a 2017 GMC Sierra?

The primary causes include a faulty NOx sensor, wiring issues such as an open or short circuit, corroded connectors, or a malfunctioning engine control module (ECM).

4. Can I drive my 2017 GMC Sierra with a P1194 code?

While it may be drivable, it's not recommended as it can lead to poor engine performance, increased emissions, and potential damage to other components if left unaddressed.

5. How is the P1194 code diagnosed on a 2017 GMC Sierra?

A technician will use a scan tool to confirm the code, inspect the NOx sensor and its wiring for damage, and test the circuit voltages to identify the root cause.

6. How do I fix the P1194 code on my 2017 GMC Sierra?

Repairs may involve replacing the NOx sensor, repairing damaged wiring or connectors, or reprogramming or replacing the ECM if it's determined to be faulty.

7. How much does it cost to fix a P1194 code on a 2017 GMC Sierra?

Repair costs vary but typically range from $300 to $800 depending on whether the NOx sensor or other components need replacement.

8. Can a dirty NOx sensor cause the P1194 code?

Yes, a dirty or contaminated NOx sensor can contribute to improper readings and trigger the P1194 code.

9. Is the P1194 code related to the oxygen sensors in the exhaust system?

No, P1194 specifically pertains to the NOx sensor, which measures nitrogen oxide levels, not the oxygen sensors that monitor air-fuel ratios.

10. Will clearing the P1194 code fix the problem on a 2017 GMC Sierra?

Clearing the code may turn off the check engine light temporarily, but the underlying issue must be resolved to prevent the code from returning.

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