NHTSA Complaint #11423856 — 2018 NEWMAR MOUNTAIN AIRE

These vehicles, built on a Spartan K3 chassis and powered by a Cummins ISX-12 engine are experiencing very high failure rates in the DEF system control head. When the control head fails, it sends error codes that result in derating engine power dramatically and/or immediate engine shut-down. This creates a very dangerous situation for anyone driving a motorhome that experiences this problem. In extreme cases, it may stop the vehicle in traffic lanes. Spartan Chassis says replacement DEF control heads are in extremely short supply and they will not provide one to a repair facility unless the affected vehicle has experienced a full derating; an initial warning message of a failing control head is deemed insufficient cause for them to provide a replacement part. Their official response is that “you must drive it until it fails before we will provide a replacement unit.” This means drivers of these motorhomes will either be subject to sudden (and, potentially very dangerous) engine shut-down, or they must cease using their expensive motorhome until such time as Spartan Chassis feels they again have a sufficient stock of replacement units. Many motorhome owners use their vehicles full time; they are their home. The inability to safely use them places a huge burden on those owners. I believe NHTSA needs to issue a recall on affected vehicles and direct Spartan Chassis to implement a software emergency bypass of the engine derating caused by a faulty DEF control head. It is my understanding that this software bypass solution already exists and is currently implemented on emergency vehicles (fire trucks) produced by Spartan Chassis.