AutoCodes – Generic – U029D

U029D 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 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 30,908

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 Oct 18, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

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

What does this mean?

What are the Possible Causes of the DTC U029D?

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?

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 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 code?

Need more information on how to fix the U029D code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U029D code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U029D Buick — Lost Communication with NOX Sensor Module 1 Malfunction
U029D Cadillac — Lost Communication with NOX Sensor Module 1 Malfunction
U029D Chevrolet — Lost Communication with NOX Sensor Module 1 Malfunction
U029D Chrysler — Lost Communication With NOX Sensor 'A'
U029D Dodge — Lost Communication With NOX Sensor 'A'
U029D Ford — Lost Communication With NOx Sensor A
U029D GMC — Lost Communication with NOX Sensor Module 1 Malfunction
U029D Jeep — Lost Communication With NOX Sensor 'A'
U029D Lincoln — Lost Communication With NOx Sensor A
U029D Mercury — Lost Communication With NOx Sensor A
U029D RAM — Lost Communication With NOX Sensor 'A'

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 Code

1. What are the common symptoms of OBDII code U029D (Lost Communication with NOX Sensor Module 1 Malfunction)?

- 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 U029D?

- The code U029D can be caused by issues such as a faulty NOX sensor, damaged wiring or connectors, software glitches, or issues with the engine control module.

3. How can I diagnose the cause of OBDII code U029D?

- Diagnosing the cause of U029D may involve using a diagnostic scanner to retrieve the trouble codes, checking the wiring and connectors for damage, and testing the NOX sensor for proper functionality.

4. Can I continue to drive my vehicle with OBDII code U029D?

- It is not recommended to drive your vehicle with the U029D code present, as it can lead to further damage and potential safety hazards. It is best to address the issue promptly.

5. How can I repair OBDII code U029D?

- Repairing U029D typically involves fixing the underlying issue causing the communication loss with the NOX sensor module. This may include replacing the NOX sensor, repairing damaged wiring, or updating software as needed.

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

- While clearing the code may temporarily turn off the check engine light, the underlying issue causing U029D will remain unresolved. It is important to address the root cause for proper vehicle performance.

7. Are there any DIY repair tips for resolving OBDII code U029D?

- DIY repair tips may include checking and cleaning the NOX sensor connectors, ensuring proper wire connections, and performing a visual inspection for any obvious signs of damage.

8. Can a mechanic help me fix OBDII code U029D?

- Yes, seeking assistance from a qualified mechanic is recommended for diagnosing and repairing OBDII code U029D to ensure the issue is properly resolved.

9. How much does it typically cost to repair OBDII code U029D?

- The cost of repairing U029D can vary depending on the specific cause of the issue, the labor rates in your area, and the cost of parts needed for the repair. It is best to consult with a mechanic for an accurate estimate.

10. Will fixing OBDII code U029D improve my vehicle's performance and fuel efficiency?

- Yes, addressing and resolving U029D can lead to improved engine performance, better fuel efficiency, and overall smoother operation of your vehicle.