As Jack studied the diagram, he noticed something peculiar. The wiring for the fuel system and the aftermarket radio seemed to intersect at a specific point. Jack had a hunch that the radio installation might be the culprit.

Jack's ears perked up at the mention of the radio. He had seen cases where aftermarket electronics had caused problems with engine wiring. He asked Alex to show him the wiring diagram for the truck's electrical system. Alex handed him a thick manual, but to their surprise, the diagram for the 4JK1 engine was not included.

From that day on, Jack kept a digital copy of the Isuzu 4JK1 wiring diagram on his phone, just in case he encountered another tricky case.