EGR / EmissionsLow ImpactDiesel

P0401 — Exhaust Gas Recirculation (EGR) Flow Insufficient

The ECU has detected that EGR flow is lower than commanded, typically via intake manifold temperature or dedicated EGR position sensors.

4+

Affected Brands

10+

ECU Platforms

2

Related Services

7

Related DTCs

Symptoms

What the driver typically experiences when P0401 is stored

!Check Engine Light
iNo noticeable drivability issues
iSlightly higher NOx emissions

Why does P0401 appear after tuning?

Triggered after EGR deactivation when the EGR monitoring diagnostics are not fully recalibrated. The ECU expects a certain flow response that no longer occurs.

How proper calibration can address P0401

WEREMAP EGR calibration deactivates both the EGR valve actuation and all associated diagnostic monitoring, including flow checks and position sensor validation.

Related Tuning Services

Relevant services for the system behind P0401

EGR OffDTC Off

Related Diagnostic Codes

Codes from the same diagnostic system as P0401

P0403Low Impact

Exhaust Gas Recirculation (EGR) Control Circuit

P0406Low Impact

Diagnostic Trouble Code P0406

P0404Low Impact

Diagnostic Trouble Code P0404

P0407Low Impact

Diagnostic Trouble Code P0407

P0405Low Impact

EGR Position Sensor Circuit Low

P0400Low Impact

Exhaust Gas Recirculation Flow

P0402Low Impact

Diagnostic Trouble Code P0402

Affected ECU Platforms

Delphi DCM6.2Bosch EDC17CP14Bosch EDC16C31Bosch EDC17C66Bosch EDC17C64Bosch EDC17-CP14Bosch EDC16U34Bosch EDC16C34Bosch EDC16CP31Bosch EDC17CP52

Commonly Affected Vehicles

AudiA3Delphi DCM6.2
MitsubishiFusoBosch EDC17CP52
VWTransporter / MultivanDelphi DCM6.2
VWTransporterDelphi DCM6.2
MBVitoBosch EDC17C66

Based on data from 4+ vehicle brands. P0401 is not limited to these models.

Frequently Asked Questions

What does P0401 mean?â–¼
The ECU has detected that EGR flow is lower than commanded, typically via intake manifold temperature or dedicated EGR position sensors.
Why does P0401 appear after ECU tuning?â–¼
Triggered after EGR deactivation when the EGR monitoring diagnostics are not fully recalibrated. The ECU expects a certain flow response that no longer occurs.
How do you prevent P0401 during remapping?â–¼
WEREMAP EGR calibration deactivates both the EGR valve actuation and all associated diagnostic monitoring, including flow checks and position sensor validation.
Which vehicles are affected by P0401?â–¼
P0401 is commonly found on Audi, Mitsubishi, VW, MB vehicles equipped with Delphi DCM6.2, Bosch EDC17CP14, Bosch EDC16C31, Bosch EDC17C66 ECU platforms.
What other codes appear alongside P0401?â–¼
P0401 frequently appears together with P0403, P0406, P0404, P0407, P0405. These related codes typically originate from the same system modification and should be addressed together in the calibration.

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