NHTSA Complaint #11634519 — 2019 FREIGHTLINER CASCADIA

I am writing to bring to your attention a potentially dangerous situation caused by what I believe to be a manufacturer design flaw with the SS 1034797 M2, 108SD, 114SD Coolant Level Sensor P/N 06-93316-002. On [XXX], one of our trucks (VIN: [XXX]) experienced a low coolant warning and an automatic engine shutdown while traveling on the interstate in a construction zone. As you can imagine, the sudden stoppage of a tractor-trailer in the traffic lanes of a freeway presents an extremely hazardous situation, not only for our driver but for all motorists in the vicinity. For us as a motor carrier, this is compounded by the likelihood of legal liability resulting from any collision involving a stationary truck in such conditions. The root cause of this incident appears to be the failure of the magnet within the surge tank to maintain its buoyancy. When the magnet sinks to the bottom of the tank, it signals the engine control module (ECM) that the coolant level is critically low, triggering an engine shutdown. While I understand the intent is to protect the engine from potential damage, this design flaw creates an unacceptably dangerous scenario—especially since, in many cases, the engine is not actually at risk of damage. In this instance, I instructed the driver to unplug and after a 15-minute period, he restarted the truck and drove to a nearby truck stop. Remarkably, the truck remains operational without the sensor repair, further underscoring the superficial nature of this issue. Unfortunately, this is not an isolated incident. We have encountered similar sensor failures across our fleet, but this particular event was the most severe. While I am not an engineer, it seems logical that the coolant level sensor should be paired with a high-temperature reading before an engine shutdown is initiated. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)