Limp mode, default, or limp home mode are operational strategies programmed into the TCM of electronic transmissions to safeguard the engine and transmission from internal damage. This mode is different from most hard faults which illuminate the MIL or check engine light, but leave the vehicle operational without limiting vehicle speed.
Limp-in mode illuminates the MIL and operates the transmission in only one forward gear (2nd or 3rd) and reverse. The vehicle should not be driven far. It causes the vehicle to start slow and the engine to rev high at speeds above twenty or thirty. This is caused by an underlying condition. It will be necessary to scan and inspect this vehicle to diagnose the fault causing this condition.