AutoCodes – Generic – U029E

U029E Code - Lost Communication with NOX Sensor Module 2 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 2, Nitrogen Oxide Sensor Module 2 harness is open or shorted, Nitrogen Oxide Sensor Module 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: U029E indicates Lost Communication with NOX Sensor Module 2 Malfunction.
Common causes: Common causes include Faulty Nitrogen Oxide (NOx) Sensor Module 2, Nitrogen Oxide Sensor Module 2 harness is open or shorted, Nitrogen Oxide Sensor Module 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 30,326

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
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Code U029E 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 U029E - Lost Communication with NOX Sensor Module 2 Malfunction - AutoCodes.com — U029E Code - Lost Communication with NOX Sensor Module 2 Malfunction

What does this mean?

What are the Possible Causes of the DTC U029E?

Faulty Nitrogen Oxide (NOx) Sensor Module 2
Nitrogen Oxide Sensor Module 2 harness is open or shorted
Nitrogen Oxide Sensor Module 2 circuit poor electrical connection

How to Fix the DTC U029E?

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 U029E 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 U029E code?

Need more information on how to fix the U029E code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U029E code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U029E Buick — Lost Communication with NOX Sensor Module 2 Malfunction
U029E Cadillac — Lost Communication with NOX Sensor Module 2 Malfunction
U029E Chevrolet — Lost Communication with NOX Sensor Module 2 Malfunction
U029E Chrysler — Lost Communication With NOX Sensor 'B'
U029E Dodge — Lost Communication With NOX Sensor 'B'
U029E GMC — Lost Communication with NOX Sensor Module 2 Malfunction
U029E Jeep — Lost Communication With NOX Sensor 'B'
U029E RAM — Lost Communication With NOX Sensor 'B'

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 U029E Code

1. What are the common symptoms of OBDII code U029E (Lost Communication with NOX Sensor Module 2 Malfunction)?

- Common symptoms include the illumination of the check engine light, reduced fuel efficiency, and potential issues with the vehicle's emissions system.

2. What can cause the OBDII code U029E to trigger?

- The code U029E typically triggers due to a malfunction or communication breakdown with the NOX (nitrogen oxide) sensor module 2 in the vehicle's exhaust system.

3. How serious is the U029E code related to the NOX sensor module 2 malfunction?

- While the vehicle may still operate, it is important to address the issue promptly to ensure proper emission control and prevent potential long-term damage to the engine or catalytic converter.

4. Can a DIY enthusiast repair the U029E code related to the NOX sensor module 2 malfunction?

- Depending on the specific cause, some DIY enthusiasts may be able to address the issue by checking and repairing wiring connections, resetting the system, or replacing the NOX sensor module 2 if necessary.

5. How can I diagnose and repair the U029E code at home?

- Diagnosing the U029E code may involve using an OBDII scanner to retrieve the specific error codes, checking the wiring and connections related to the NOX sensor module 2, and potentially replacing the faulty sensor module.

6. Will driving with the U029E code present cause further damage to my vehicle?

- Continuing to drive with the U029E code present may lead to reduced fuel efficiency and potentially damage the vehicle's emissions system over time, so it is advisable to address the issue promptly.

7. Are there any safety concerns associated with the U029E code related to the NOX sensor module 2 malfunction?

- While the U029E code itself does not pose immediate safety risks, addressing the underlying issue is important to ensure the vehicle's emission control system functions correctly and to prevent environmental impact.

8. How much does it typically cost to repair the U029E code related to the NOX sensor module 2 malfunction at a mechanic?

- The cost of repairing the U029E code can vary depending on the cause of the issue, but it may involve labor costs for diagnosis, potential sensor module replacement, and any necessary repairs to the wiring or connections.

9. Can the U029E code related to the NOX sensor module 2 malfunction be a recurring issue?

- If the underlying cause of the U029E code is not properly addressed, it can potentially recur, leading to persistent check engine light illuminations and ongoing issues with the vehicle's emissions system.

10. Is it safe to drive my vehicle with the U029E code related to the NOX sensor module 2 malfunction temporarily ignored?

- While driving with the U029E code may not immediately affect the vehicle's drivability, it is recommended to address the issue promptly to ensure optimal performance and emission control.