2021-2022 Nissan Sentra MIL On with DTC P0401 P0404

Nissan has released Technical Service Bulletin (TSB) NTB22-067A to address instances where the Malfunction Indicator Lamp (MIL) illuminates in 2021-2022 Nissan Sentra vehicles. This TSB specifically targets vehicles that have DTC P0401 and/or P0404 stored in the Engine Control Module (ECM).

This bulletin, which supersedes the original NTB22-067 dated July 29, 2022, provides a software update to correct the underlying cause of these diagnostic trouble codes. Owners experiencing a Check Engine Light with these specific codes should consult their Nissan dealer for diagnosis and repair.

Symptoms

Owners of affected 2021-2022 Nissan Sentra vehicles may observe the following symptoms:

• The Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light, is illuminated on the dashboard.
• Diagnostic Trouble Code (DTC) P0401, indicating "EGR A FLOW INSUFFICIENT", is stored in the ECM.
• Diagnostic Trouble Code (DTC) P0404, indicating "EGR A CONTROL", is stored in the ECM.
• There are no noticeable drivability concerns associated with these codes.

Fault Codes / DTCs

This TSB specifically addresses the following diagnostic trouble codes:

Diagnosis and Trigger Conditions

To confirm if this bulletin applies, a qualified technician will first use the C-III plus diagnostic tool to confirm the current ECM part number. The bulletin provides a table of specific ECM part numbers (e.g., 23710-6LB3B, 23710-6LX3B) that are eligible for the reprogram. If the vehicle's ECM part number matches one listed in the TSB, the reprogramming procedure can proceed. If the part number does not match, this bulletin does not apply, and further diagnostic steps would be required.

Repair Procedure Summary

The repair for the Nissan Sentra P0401 P0404 issue involves reprogramming the Engine Control Module (ECM). This is a software update designed to correct the conditions that trigger these specific DTCs.

Before initiating the reprogramming, technicians must follow several critical steps to prevent damage to the control unit:

• Connect the AC Adapter to the CONSULT PC.
• Ensure the CONSULT PC is connected to the internet via Wi-Fi or a network cable.
• Verify that ASIST on the CONSULT PC is synchronized and all software updates are installed.
• Turn off all external Bluetooth devices (e.g., cell phones, printers) within range of the CONSULT PC and the Vehicle Interface (VI) to prevent interruption.
• Turn off all vehicle electrical loads and turn on the hazard warning lamps.
• Connect a battery maintainer or smart charger, set to reflash mode, to ensure the battery voltage remains between 12.0 V and 15.5 V during the process.

After reprogramming, several post-reprogramming procedures are required, including performing "Throttle Valve Closed Position", "Idle Air Volume Learning", "Accelerator Closed Position", and "DTC Erase". The