2011 Mack CXU600
Eaton 8 speed
Customer states truck would intermittently not start, said driver could wiggle ECM connector and got it to start once. Pulled into shop and check all the fuses, all were ok. confirmed is would not start. wiggled on harness for a while and was unable to get truck to turn over. un plugged and checked connectors and all were ok. sometimes it would just start to engage the starter then stop. checked and confirmed I am getting power to starter, confirmed soft start works. can ground out soft start and truck will TURN right over but no start. wiring diagram shows a starter relay control driver circuit to ground out starter relay directly form ECM. it is not sending signal to ground. checked circuit for shorts to power, ground, resistance, load tested and even ran a temporary new circuit to no avail. I do now know the logic behind this starting system, un plugged and checked the oil temp sensor as I read this could cause it as well. anyone else run into this issue? customer is insisting it is the engine wiring harness but I'm hard pressed to just replace parts. checked for codes and have codes. INFORMATION DISPLAY PPID 278 Aftertreatment Reagent level FMI 9 abnormal update rate, active, 1 count. INFORMATION DISPLAY PSID 200 data link MID 128, FMI 9 abnormal update rate, active, 1 count. VECU PSID 200 data link MID 128, FMI 9 abnormal update rate, active, 5 counts.