  The unknown $\gamma$-ray excess in the northwest region of Arp 220 was
revisited by analyzing $\sim$11.8 years of the \textit{Fermi} Large Area
Telescope (\textit{Fermi}-LAT) data in this study. We found that its photon
flux was approximately three times higher than that of the previous study in
the 0.2-100 GeV band, and the corresponding significance level$\sim8.15\sigma$
was approximately four times higher than before. The light curves of 15 and 45
time bins from the whole time all showed two active periods, and the
variability of the second period was more significant than that of the first
period. The spectral indices from the two active periods were not statistically
different and were close to the range of $\gamma$-ray flat-spectrum radio
quasars observed by \textit{Fermi}-LAT. Because the position of CRATES
J153246+234400 was consistent with the best-fit position of our analysis, we
suggest that CRATES J153246+234400 is more likely a $\gamma$-ray counterpart
for the variational region. For Arp 220, there was no significant variability
in the $\gamma$-ray emission.
