U029E A module on the network stopped hearing the second (downstream) NOx sensor module

Lost communication with NOx sensor B

U029E in short

U029E means the engine computer lost communication with the second NOx sensor module in a diesel exhaust. GM and Ford bulletins name water in the sensor connector, a Silverado owner fixed the code with a new downstream sensor, and trucks can derate. Have it checked soon.

Diesel trucks use a NOx sensor before and after the aftertreatment. U029E is stored when the engine computer loses the second sensor module. Silverado owners read it as "NOx sensor module 2 communication lost".

GM bulletin 17-NA-219 describes moisture past a torn or missing seal in the sensor connector, and Ford TSB 20-2067 names water intrusion for 2017-2020 Super Duty trucks. A Silverado 2500 owner solved "Exhaust Fluid Service" and "Reduced Speed" messages by replacing the downstream sensor.

Ford SSM 50455 covers a different case: some 2021 Super Duty trucks built in July 2021 stored U029E after a PCM programming step did not finish. Volkswagen also has a diagnostic tip for U029E on 2015 diesel models during a campaign.

Most likely causes

  1. Failed downstream NOx sensor or module

    Supported by vehicle data
    Why it ranks here
    A 2017 Silverado 2500 owner cleared U029E, exhaust fluid and reduced speed messages by replacing the downstream sensor after a month of trouble.
    What would change this
    Rises if the connector is clean and the sensor is the only thing not answering. Falls if wiring or software is at fault.

  2. Water or corrosion in the sensor connector or harness

    Supported by vehicle data
    Why it ranks here
    GM 17-NA-219 and Ford TSB 20-2067 both name moisture or water intrusion for this code on listed trucks.
    What would change this
    Rises if moisture, corrosion or a bad seal is seen. Falls if dry.

  3. Incomplete PCM programming (2021 Super Duty built 7-11 July 2021)

    Supported by vehicle data
    Why it ranks here
    Ford SSM 50455 says trucks in that build window can end up with U029E when programming did not finish.
    What would change this
    Rises on trucks built in that window right after a programming event. Falls on other build dates.
    How to test the engine control module (ecm / pcm)

  4. Power or network fault affecting several modules

    Possible — needs testing
    Why it ranks here
    A 2022 Silverado 2500 with active U029D and U029E needed jump starts, and a 2017 truck stored many other lost-communication codes.
    What would change this
    Rises when many modules log faults. Falls if only the NOx codes are stored.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes and note whether U029D, U02A3 or reductant and particulate sensor codes are stored too.

    Low riskTool: scan tool

  2. Have the downstream NOx sensor connector and harness inspected for moisture, corrosion and seal damage, then test the sensor module.

    Best left to a shop

    Warning:The exhaust system is hot after driving; let it cool, and leave diesel emissions repairs to a shop.

Symptoms

  • Reduced speed message
  • Exhaust fluid service message
  • Power loss while driving Gets more serious: stop and have it checked.

How to fix

On your vehicle

Ford

  • 2017–2021 · F-250 Super Duty

    Supported by vehicle data

    Ford bulletins name water intrusion and a 2021 build-window programming problem for U029E.

  • TSB 20-2067Status unverified

    6.7L Super Duty MIL with U029D, U029E, P22A7 and/or P2209

    2017–2020f-250-super-duty, f-350-super-duty, f-450-super-duty · NHTSA 10187826

    Builds up to 10-Jun-2020; water intrusion is named. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM 50455Status unverified

    2021 6.7L Super Duty built 7-11 July 2021, U029E after programming

    2021f-250-super-duty, f-350-super-duty, f-450-super-duty · NHTSA 10208078

    PCM reprogramming or module installation is not recommended in that build window at that date. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2014–2022 · Silverado 2500 HD

    Supported by vehicle data

    Owners report U029E with reduced speed and exhaust fluid messages; one cleared it with a new downstream sensor.

  • 2016–2018 · Colorado

    Supported by vehicle data

    GM diagnostic tip names moisture past a connector seal.

  • 17-NA-219Status unverified

    MIL with P249D, P249E, U029D, U029E

    2016–2018colorado, express, silverado-1500, silverado-2500-hd, silverado-3500-hd · issued · NHTSA 10190267

    Moisture past a torn or missing seal in the NOx sensor harness connector. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Volkswagen

  • TT 01 18 09Status unverified

    Diagnostic tip when performing campaign 23Y8 should DTC U029E store in ECM memory

    2015beetle, golf, golf-sportwagen · NHTSA 10150805

    Only the title was in the NHTSA summary. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • U029DA module on the network stopped hearing the first (upstream) NOx sensor module

    Same system Supported by vehicle data

    U029D is the matching lost-communication code for the first NOx sensor module and is often stored with U029E.

All Module network (CAN bus) communication codes

Sources and review

  1. NHTSA complaint ODI 11282684: 2014 Chevrolet Silverado 2500 — NHTSA (owner complaint)
  2. NHTSA complaint ODI 11600634: 2017 Chevrolet Silverado 2500 — NHTSA (owner complaint)
  3. GM 17-NA-219 (NHTSA 10190267): MIL with P249D, P249E, U029D, U029E — NHTSA (manufacturer communication)
  4. NHTSA complaint ODI 11603488: 2022 Chevrolet Silverado 2500 — NHTSA (owner complaint)
  5. Ford TSB 20-2067 (NHTSA 10187826): 2017-2020 Super Duty 6.7L MIL with U029D, U029E, P22A7 and/or P2209 — NHTSA (manufacturer communication)
  6. Ford SSM 50455 (NHTSA 10208078): 2021 Super Duty 6.7L built 7-11 July 2021, U029E — NHTSA (manufacturer communication)
  7. NHTSA complaint ODI 11595734: 2017 Chevrolet Silverado 2500 — NHTSA (owner complaint)
  8. NHTSA complaint ODI 11599344: 2017 Chevrolet Silverado 2500 — NHTSA (owner complaint)
  9. Volkswagen TT 01 18 09 (NHTSA 10150805): diagnostic tip when doing campaign 23Y8 and U029E stores in the ECM — NHTSA (manufacturer communication)
Last reviewed
Written by
Saurabh K.
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