J1939 Voltage Levels: What Are Normal Ranges for CAN High, CAN Low, and Battery Power?
Last month, a fleet manager in Alberta sent me a photo of his multimeter. The reading on CAN High was 4.8 volts. “Is this why my 2023 Peterbilt keeps throwing SPN 639?” he asked. That single reading told me the whole story. The bus was shorted to battery power. Until someone traced that short, he would keep swapping ECUs […]