2011 Maxxforce DT won't crank over. The crank relay on the firewall has voltage to pins 30 and 85 when the key is in the crank position. Pin 86 on the crank relay has no ground signal. If I ground pin 86 the bus will start and run. ISIS shows this ground signal comes from pin 7 on connector 6020 on the engine ECM. Allison Doc shows the trans is in nuetral and does change to drive or reverse when commanded. I haven't been able to find the wiring and connector composit pin outs from the trans to the ECM. Allison now calls the NSBU Internal Mode Switch. Bus does not have the thermal overcrank option.
problem found. wire between TCM and ECM had open circuit about 4" from TCM. disconnected the connector at the TCM and connector 6020 at the ECM. checked with ohmmeter from Pin 41 at the TCM to Pin 65 at the ECM and found open circuit.
11 Maxxforce DT won't crank
Posted - 04/11/2014 : 6:33:59 PM
