IllustrationTwo issues, both resulting in derating to 5 mph on a busy freeway. The DEF sensor has had repeated failures, resulting in 7 generations of DEF sensors, all of which have had repeated failures. Without reprogramming by Cummins, a DEF simulator, or DEF sensor replacement, the engine derates to 5mph upon 2 restarts. This results in…
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Two issues, both resulting in derating to 5 mph on a busy freeway. The DEF sensor has had repeated failures, resulting in 7 generations of DEF sensors, all of which have had repeated failures. Without reprogramming by Cummins, a DEF simulator, or DEF sensor replacement, the engine derates to 5mph upon 2 restarts. This results in a dangerous driving situation unless the vehicle is towed. The second issue is a faulty wiring harness in all Cummins ISV 5.0 engines, used in Nissan Pickups, buses, and Tiffin Breeze motorhomes from 2017-2019. The wiring harness was designed with injector wires that were too short, which caused injectors to intermittently fail, causing the engine to derate on the fly, causing a dangerous driving situation. In June of 2022, Cummins issued a TSB regarding this but no recall was initiated. This issue with the wiring harness and injectors is now linked to the premature engine failure of hundreds of these engines, which results in an immediate stopping of the vehicle in potentially high traffic situations. Neither Cummins nor Tiffin are acknowledging this, or replacing engines unless in warranty. For Tiffin Breeze motorhomes, 3 of the 2017 engines have failed just after warranty expiration that I personally know of. This has occurred in as little as 20,000+ miles. Tiffin and Cummins should inspect all engines that have had documented harness/injector errors for potentially damaged/overheated crankshafts, as broken crankshafts have caused the engine failures.