Check Engine Light Leads to Stop Engine Light

Without being able to pull the fault codes there isn't much one can do to correct. Not all the dash gauges and indicators get data from the same sensor the engine or transmission computer uses. Could be something as simple as an intermittent ground on the coolant temp sensor for the engine computer but the dash gauge is from a second sensor. The computer is going to do whatever it can to protect the engine from catastrophic damage to include leaving you stranded.

Besides calling for a tow he could contact Cummins Care at 1-800-DIESELS (1-800-343-7357).