CMAQ error at AQCHEM



I am getting the following error while running CMAQv521. I am running for whole September of 2016 and CMAQ crashed on 13th.
Does anyone have any idea why I am getting this error?
I am running CMAQ with modified IC and BC files to values 1E-10 to minimize the influence of BC conditions.


 *** ERROR ABORT in subroutine AQCHEM on PE 091          
 Maximum AQCHEM total iterations exceeded


When I have had this error, it has always been a result of something going wrong elsewhere in the model or its input data, such that tweaking the AQCHEM convergence criteria or number of allowable iterations was not the right way to go. Most recently, this happened to me when I had bad (unreasonably large) precipitation values in the METCRO2D file.