AutoCodes – GMC – U029D GMC

U029D GMC Code - Lost Communication with NOX Sensor Module 1 Malfunction

Quick Answer

The reductant system uses two Nitrogen Oxide (NOx) sensors to monitor the amount of NOx in the engine's exhaust gas. Common causes include Faulty Nitrogen Oxide (NOx) Sensor Module 1, Nitrogen Oxide Sensor Module 1 harness is open or shorted, Nitrogen Oxide Sensor Module 1 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: U029D GMC indicates Lost Communication with NOX Sensor Module 1 Malfunction.
Common causes: Common causes include Faulty Nitrogen Oxide (NOx) Sensor Module 1, Nitrogen Oxide Sensor Module 1 harness is open or shorted, Nitrogen Oxide Sensor Module 1 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 2,263

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 Oct 18, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U029D GMC Description

The reductant system uses two Nitrogen Oxide (NOx) sensors to monitor the amount of NOx in the engine's exhaust gas. The first sensor is located at the outlet of the turbocharger and monitors the engine out NOx level. The second NOx sensor is located between the Selective Catalytic Reduction (SCR) and the Diesel Particulate Filter (DPF) and monitors NOx levels downstream of the SCR. The second NOx sensor also provides the Engine Control Module (ECM) with information on the exhaust oxygen level during DPF regeneration.
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 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 (DEF) or reductant added by varying the reductant injector duty cycle in response to changes in engine exhaust out 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.

OBDII Code U029D GMC - Lost Communication with NOX Sensor Module 1 Malfunction - AutoCodes.com — U029D GMC Code - Lost Communication with NOX Sensor Module 1 Malfunction

What does this mean?

What are the Possible Causes of the DTC U029D GMC?

Faulty Nitrogen Oxide (NOx) Sensor Module 1
Nitrogen Oxide Sensor Module 1 harness is open or shorted
Nitrogen Oxide Sensor Module 1 circuit poor electrical connection

How to Fix the DTC U029D 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 U029D 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 U029D GMC code?

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Need Help with the Code?

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Information for Specific GMC Models

U029D 2014 GMC Sierra — Lost Communication with NOX Sensor Module 1 Malfunction
U029D 2015 GMC Sierra — Lost Communication with NOX Sensor Module 1 Malfunction
U029D 2016 GMC Sierra — Lost Communication with NOX Sensor Module 1 Malfunction
U029D 2017 GMC Sierra — Lost Communication with NOX Sensor Module 1 Malfunction
U029D 2018 GMC Sierra — Lost Communication with NOX Sensor Module 1 Malfunction

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 U029D GMC Code

1. What are the common symptoms of OBDII code U029D GMC?

- Common symptoms include poor engine performance, reduced fuel efficiency, illuminated Check Engine Light, and difficulty passing emissions tests.

2. What could cause the U029D GMC code to appear?

- The code is typically triggered by a malfunction in the NOX (nitrogen oxide) sensor module or a communication issue between the sensor module and the vehicle's onboard computer.

3. How can I diagnose the U029D GMC code?

- Diagnosis involves using an OBDII scanner to retrieve the specific fault code and then conducting a thorough inspection of the NOX sensor module and its connections for any visible damage or corrosion.

4. Can I continue driving my vehicle with the U029D GMC code present?

- It is not recommended to continue driving with this code activated, as it can lead to further damage to the emissions control system and potentially affect the engine's performance.

5. What are some repair tips for resolving the U029D GMC code?

- Repair options may include replacing the NOX sensor module, repairing damaged wiring or connectors, resetting the fault code with an OBDII scanner, and ensuring proper communication between the sensor module and the vehicle's computer.

6. Is it possible to reset the U029D GMC code without fixing the underlying issue?

- While it is possible to reset the code temporarily, the Check Engine Light is likely to reappear if the root cause of the problem is not addressed.

7. How much does it typically cost to repair the U029D GMC code?

- Repair costs can vary depending on the extent of the issue, the specific parts needing replacement, and whether the repair is done at a dealership or an independent mechanic. It's advisable to obtain a few quotes for accurate pricing.

8. Are there any preventative measures to avoid the U029D GMC code in the future?

- Regular maintenance, such as inspecting and cleaning sensor connections, checking for signs of wear or damage, and using high-quality fuel, can help prevent issues that may trigger this code.

9. Can a DIY enthusiast fix the U029D GMC code at home?

- While some basic troubleshooting steps can be performed at home, diagnosing and repairing the U029D code may require advanced technical knowledge and specialized tools. It's recommended to consult a professional mechanic for accurate diagnosis and repair.

10. How long does it typically take to resolve the U029D GMC code?

- The repair time can vary depending on the exact cause of the issue, availability of parts, and the mechanic's workload. In general, resolving the U029D code may take a few hours to a day, depending on the complexity of the repair.