
A 2022 Freightliner Cascadia near Highway 123 in San Marcos, TX was diagnosed by a mobile diesel mechanic for a persistent coolant sensor fault after the sensor had already been replaced — the root cause was identified as a failed coolant reservoir, which the owner declined to have replaced at that time; the fault code was cleared with a scan tool, and the owner was notified in writing that the warning would return shortly without the reservoir repair.



