OBD2 Breakout Box Jumper Pin 4 to Pin 5: The Ground Loop That Destroys Engine Control Modules
The 2016 Freightliner Cascadia rolled back into the bay two days after we replaced the engine control module. Same CAN bus failure. The new ECU was already dead. The breakout box on the floorboard still had the jumper across Pin 4 and Pin 5 from a bench test earlier that week. We had tied chassis ground and signal ground together before the module ever saw them. The […]