AutoCodes – GMC – P1194 2015 GMC Sierra

P1194 2015 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 2015 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 155

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 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1194 2015 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 2015 GMC Sierra - O2 Low Reference Circuit High Voltage (NOx Sensor 1) - AutoCodes.com — P1194 2015 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 2015 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 2015 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 2015 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 2015 GMC Sierra code?

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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 P1194 2015 GMC Sierra Code

1. What does OBDII code P1194 mean on a 2015 GMC Sierra?

Code P1194 indicates a problem with the O2 Low Reference Circuit High Voltage for NOx Sensor 1, typically related to the exhaust system's monitoring components.

2. What are the common symptoms of code P1194 on a 2015 GMC Sierra?

Symptoms may include the check engine light turning on, reduced fuel efficiency, poor engine performance, and difficulty passing emissions tests.

3. What causes OBDII code P1194 on a 2015 GMC Sierra?

Common causes include a faulty NOx sensor, wiring issues such as damaged or corroded connectors, or problems with the ECM (Engine Control Module).

4. How does a faulty NOx sensor lead to code P1194?

A malfunctioning NOx sensor may send incorrect voltage signals to the ECM, triggering the high-voltage reading in the O2 reference circuit.

5. Can driving with code P1194 damage my 2015 GMC Sierra?

Driving with this code for an extended period may lead to increased emissions and potential damage to the catalytic converter or other exhaust components.

6. How do I diagnose code P1194 on my GMC Sierra?

Diagnosis involves using an OBDII scanner, inspecting the NOx sensor wiring and connectors, and testing the sensor voltage output.

7. How can I fix code P1194 on a 2015 GMC Sierra?

Repairs may include replacing the NOx sensor, repairing or replacing damaged wiring, cleaning connectors, or updating the ECM software.

8. How much does it cost to repair code P1194 on a GMC Sierra?

Repair costs vary but typically range from $200 to $600 depending on whether parts like the NOx sensor or wiring need replacement.

9. Can a loose connector cause code P1194 on a 2015 GMC Sierra?

Yes, a loose or corroded connector can disrupt the voltage signal, leading to the P1194 code.

10. Do I need special tools to fix code P1194 on a GMC Sierra?

Basic tools like a multimeter and OBDII scanner are often sufficient for diagnosis, but replacing parts like the NOx sensor may require specialized tools.