AutoCodes – GMC – P1004 GMC

P1004 GMC 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 GMC 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 708

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

What does this mean?

What are the Possible Causes of the DTC P1004 GMC?

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 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 P1004 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 P1004 GMC code?

Need more information on how to fix the P1004 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

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Information for Specific GMC Models

P1004 2014 GMC Sierra — NOx Sensor 2 Slow Response
P1004 2015 GMC Sierra — NOx Sensor 2 Slow Response
P1004 2016 GMC Sierra — NOx Sensor 2 Slow Response
P1004 2017 GMC Sierra — NOx Sensor 2 Slow Response
P1004 2018 GMC Sierra — NOx Sensor 2 Slow Response

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 GMC Code

1. What are the common symptoms of OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

The common symptoms of code P1004 include reduced engine performance, increased fuel consumption, and the illumination of the check engine light.

2. What can cause the OBDII code P1004 GMC to trigger (NOx Sensor 2 Slow Response)?

Possible causes of code P1004 include a faulty NOx sensor, wiring issues, exhaust leaks, or a malfunctioning catalytic converter.

3. How serious is the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

While the vehicle may still be operable with this code, it is important to address it promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

4. How can I diagnose the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

Diagnosing code P1004 typically involves using a scan tool to retrieve the code, inspecting the NOx sensor and its wiring, checking for exhaust leaks, and testing the catalytic converter.

5. Can I drive my vehicle with the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

It is generally safe to drive the vehicle with this code, but it is recommended to address the underlying issue as soon as possible to prevent further complications.

6. What are some repair tips for fixing the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

Repair tips for resolving code P1004 include checking and replacing the NOx sensor, repairing any damaged wiring, fixing exhaust leaks, and inspecting the catalytic converter for proper function.

7. How much does it cost to repair the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

The cost of repairing code P1004 can vary depending on the underlying issue, but it may range from a few hundred to over a thousand dollars, including parts and labor.

8. Can a DIY enthusiast fix the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

While some aspects of diagnosing and repairing code P1004 may be tackled by a DIY enthusiast with the right tools and knowledge, certain repairs may require professional expertise.

9. How long does it take to repair the OBDII code P1004 GMC (NOx Sensor 2 Slow Response)?

The repair time for code P1004 can vary based on the specific issue and the expertise of the technician, but it may take a few hours to a full day to complete the repairs.

10. Will resetting the OBDII code P1004 GMC (NOx Sensor 2 Slow Response) make it go away permanently?

Resetting the code may temporarily turn off the check engine light, but if the underlying issue is not fixed, the code is likely to reappear. It is crucial to address the root cause of the problem for a permanent solution.