# MEGAN 3.1 Error : running run.mgn2mech.v31.csh

**URL:** <https://forum.cmascenter.org/t/megan-3-1-error-running-run-mgn2mech-v31-csh/5832>\
**Category:** MEGAN\
**Tags:** cmaq, emissions\
**Created:** [May 28, 2025, 3:15pm UTC](https://forum.cmascenter.org/t/megan-3-1-error-running-run-mgn2mech-v31-csh/5832 "2025-05-28T15:15:43Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![summer](https://avatars.discourse-cdn.com/v4/letter/s/bb73d2/32.png) [@summer](https://forum.cmascenter.org/u/summer)\
**Post date:** [May 28, 2025, 3:15pm UTC](https://forum.cmascenter.org/t/megan-3-1-error-running-run-mgn2mech-v31-csh/5832/1 "2025-05-28T15:15:43Z")

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Dear Professors,  
I am encountering some issues while running MEGAN3.1 and would greatly appreciate your assistance.  
In the ‘run.mgn2mech.v31.csh’ file within the ‘MEGAN31\_Calc\_Code’ module, I set the mechanism to **SAPRC07**. However, this results in an error. Notably, when I previously ran it with the **CB6X** mechanism, the output was generated successfully and without errors.  
The specific error messages are shown in the attached screenshot. I am currently unsure how to resolve this issue and am under some time pressure. I would be very grateful for your help.  
Thank you.

 ![image](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/4/47e9a8efec387fceee2adf011f54f001df4b0e0c.png)