Emissions / AuxiliaryLow ImpactPetrol

P0491 — Diagnostic Trouble Code P0491

OBD-II diagnostic code P0491 relates to the emissions / auxiliary system. This code is logged when the ECU detects a parameter outside its expected operating range.

4+

Affected Brands

12+

ECU Platforms

1

Related Services

1

Related DTCs

Symptoms

What the driver typically experiences when P0491 is stored

!Check Engine Light
iFailed emissions test
iNo major drivability impact

Why does P0491 appear after tuning?

This code may appear after ECU modifications when the affected system monitoring has not been fully recalibrated for the new operating parameters.

How proper calibration can address P0491

WEREMAP professional calibrations include comprehensive diagnostic management for all affected systems, preventing unnecessary fault codes while maintaining safe operation.

Related Tuning Services

Relevant services for the system behind P0491

DTC Off

Related Diagnostic Codes

Codes from the same diagnostic system as P0491

P0492Low Impact

Diagnostic Trouble Code P0492

Affected ECU Platforms

Bosch MED17.1.1Bosch MED17.1.6Bosch MED9.1Bosch MG1CS001Siemens/Continental SIMOS16.21Siemens/Continental simos18.1Bosch MED17.9.7 / ME17.8.32Bosch MED17.1.11Bosch SIM271DEBosch MED17.1.15Siemens/Continental SIMOS8.5Siemens/Continental SIMOS8.3

Commonly Affected Vehicles

VWTiguanBosch MG1CS001
AudiQ7Siemens/Continental SIMOS16.21
VWTouaregBosch MED17.1.6
AudiA8Bosch MED17.1.1
VWGolfSiemens/Continental simos18.1
McLarenSuper SeriesBosch MED17.9.7 / ME17.8.32
Porsche911Bosch MED17.1.11
AudiRS5Bosch MED17.1.1

Based on data from 4+ vehicle brands. P0491 is not limited to these models.

Frequently Asked Questions

What does P0491 mean?â–¼
OBD-II diagnostic code P0491 relates to the emissions / auxiliary system. This code is logged when the ECU detects a parameter outside its expected operating range.
Why does P0491 appear after ECU tuning?â–¼
This code may appear after ECU modifications when the affected system monitoring has not been fully recalibrated for the new operating parameters.
How do you prevent P0491 during remapping?â–¼
WEREMAP professional calibrations include comprehensive diagnostic management for all affected systems, preventing unnecessary fault codes while maintaining safe operation.
Which vehicles are affected by P0491?â–¼
P0491 is commonly found on VW, Audi, McLaren, Porsche vehicles equipped with Bosch MED17.1.1, Bosch MED17.1.6, Bosch MED9.1, Bosch MG1CS001 ECU platforms.
What other codes appear alongside P0491?â–¼
P0491 frequently appears together with P0492. These related codes typically originate from the same system modification and should be addressed together in the calibration.

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