AutoCodes – GMC – P1004 2017 GMC Sierra

P1004 2017 GMC Sierra Code - NOx Sensor 2 Slow Response

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: P1004 2017 GMC Sierra indicates NOx Sensor 2 Slow Response.
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 169

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
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Code P1004 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 P1004 2017 GMC Sierra - NOx Sensor 2 Slow Response - AutoCodes.com — P1004 2017 GMC Sierra Code - NOx Sensor 2 Slow Response

What does this mean?

What are the Possible Causes of the DTC P1004 2017 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 P1004 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 P1004 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.

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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 P1004 2017 GMC Sierra Code

1. What does the OBDII code P1004 mean on a 2017 GMC Sierra?

The P1004 code indicates a "NOx Sensor 2 Slow Response," meaning the downstream NOx sensor is not responding as expected to changes in exhaust gas composition.

2. What are the symptoms of the P1004 code?

Common symptoms include an illuminated check engine light, decreased fuel efficiency, potential power loss, and increased emissions.

3. What causes the P1004 code to appear?

The code can be caused by a faulty NOx sensor, wiring issues, exhaust leaks, soot buildup on the sensor, or a malfunctioning engine control module (ECM).

4. How can I diagnose the P1004 code on my GMC Sierra?

Start by inspecting the NOx sensor wiring for damage, checking for exhaust leaks, and using a scan tool to monitor the NOx sensor readings to see if they are within the expected range.

5. Can I drive my 2017 GMC Sierra with the P1004 code?

While the vehicle may still be drivable, itâ€™s not recommended as it can lead to poor performance, increased emissions, and potential damage to the catalytic converter.

6. How do I fix the P1004 code on a 2017 GMC Sierra?

Repairs may include replacing the faulty NOx sensor, repairing damaged wiring, cleaning soot buildup, or addressing exhaust leaks. In some cases, the ECM may need reprogramming.

7. How much does it cost to fix the P1004 code?

Replacing a NOx sensor can cost between $300 and $800, depending on labor and parts. Additional repairs like fixing wiring or exhaust leaks can increase the cost.

8. Can a clogged DEF system cause the P1004 code?

Yes, a clogged Diesel Exhaust Fluid (DEF) injector or system can affect NOx sensor performance and contribute to this code.

9. How can I prevent the P1004 code from recurring?

Regularly maintain the exhaust and DEF systems, use high-quality DEF fluid, and address any engine performance issues promptly to prevent strain on the NOx sensors.

10. What is the difference between NOx Sensor 1 and NOx Sensor 2?

NOx Sensor 1 is located upstream of the SCR (Selective Catalytic Reduction) system, while NOx Sensor 2 is located downstream to monitor the effectiveness of the SCR in reducing NOx emissions.