AutoCodes – GMC – P1194 GMC

P1194 GMC 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 GMC 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 402

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 29, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1194 GMC 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 GMC - O2 Low Reference Circuit High Voltage (NOx Sensor 1) - AutoCodes.com — P1194 GMC Code - O2 Low Reference Circuit High Voltage (NOx Sensor 1)

What does this mean?

What are the Possible Causes of the DTC P1194 GMC?

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 GMC?

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 GMC 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 GMC code?

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

Need Help with the Code?

Get the P1194 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P1194 2014 GMC Sierra — O2 Low Reference Circuit High Voltage (NOx Sensor 1)
P1194 2015 GMC Sierra — O2 Low Reference Circuit High Voltage (NOx Sensor 1)
P1194 2016 GMC Sierra — O2 Low Reference Circuit High Voltage (NOx Sensor 1)
P1194 2017 GMC Sierra — O2 Low Reference Circuit High Voltage (NOx Sensor 1)
P1194 2018 GMC Sierra — O2 Low Reference Circuit High Voltage (NOx Sensor 1)

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 GMC Code

1. What are the common symptoms of OBDII code P1194 (O2 Low Reference Circuit High Voltage)?

- Common symptoms include poor engine performance, decreased fuel efficiency, and the illumination of the check engine light.

2. What are the possible causes of OBDII code P1194 in a GMC vehicle?

- The code P1194 in a GMC vehicle is typically caused by a faulty NOx sensor, damaged wiring or connectors, or issues with the vehicle's engine control module (ECM).

3. How can I diagnose OBDII code P1194 related to the O2 Low Reference Circuit High Voltage in my GMC vehicle?

- Diagnosing this code involves using a scan tool to retrieve the specific fault code, inspecting the NOx sensor and its wiring, and checking for any visible signs of damage or corrosion.

4. Can a DIY enthusiast repair OBDII code P1194 in a GMC vehicle?

- While some basic troubleshooting steps can be performed by a DIY enthusiast, repairing OBDII code P1194 may require specialized tools and expertise, making it advisable to seek professional help.

5. Are there any quick repair tips for resolving OBDII code P1194 in a GMC vehicle?

- Quick repair tips may include checking and cleaning the sensor connectors, ensuring proper sensor grounding, and confirming the integrity of the sensor wiring.

6. How critical is it to address OBDII code P1194 in a GMC vehicle promptly?

- It is important to address OBDII code P1194 promptly to prevent potential damage to the vehicle's emissions system and to ensure optimal engine performance and fuel efficiency.

7. Can driving with OBDII code P1194 present any risks to the vehicle's engine or emissions system?

- Continuing to drive with OBDII code P1194 may lead to increased emissions, decreased fuel efficiency, and potential damage to the vehicle's engine or emissions system over time.

8. Is resetting the check engine light a sufficient solution for OBDII code P1194 in a GMC vehicle?

- Resetting the check engine light without addressing the underlying issue causing OBDII code P1194 is not a permanent solution and may result in the code reoccurring.

9. How much does it typically cost to repair OBDII code P1194 in a GMC vehicle at a professional repair shop?

- The cost of repairing OBDII code P1194 in a GMC vehicle at a professional repair shop can vary depending on the specific cause of the issue, but it may range from a few hundred to a thousand dollars.

10. Is it recommended to continue driving a GMC vehicle with OBDII code P1194 until it can be repaired?

- It is generally not recommended to continue driving a GMC vehicle with OBDII code P1194, as doing so may lead to further damage and potentially result in more costly repairs in the long run.