11 - Transmission general faults.
15 - Coolant temperature (CTS) signal below normal range.
55 - ECM fault.
It would be important to resolve the 55 error first, since that could contribute to the other codes being generated. Verify that the ECM connectors are clean and tight. It would be best to disconnect battery power first, then remove and insect the ECM connectors. While the ECM is disconnected, open the access cover and inspect the interior for moisture or corrosion.