After stalling at Tunnel #2, UP's Fresno to West Colton manifest train starts to roll up the steep grade of Allard between Bealville and Caliente. After stopping at Caliente to let two northbound trains by, the 60 car long manifest train started to lose power effort from their 4th motor; UP 8150. As they struggle out of Tunnel #1, the conductor worked from the 4th motor, relaying information from the computer screens to the engineer on the headend.
Once they stalled at Tunnel #2, the crew was able to noticed that the 4th motor was not responding the same way as the rest of the motors in the train. When the engineer would give the train power, the 4th motor would not match the same throttle notch as the rest of the consist. This resulted in the crew, and UP Mechanical in Omaha, NE on the radio, coming to the conclusion that there was bad MU cable between the 3rd and 4th motor. Once the rapid responder arrived with a new MU cable, the train was able to take off without a problem.