No COMM From Micro to ENCU
engine
Description
The main microprocessor cannot communicate with the engine control unit over the CAN bus, and the unit shuts down and alarms.
Activation Conditions
Main microprocessor cannot communicate with the engine control unit over the CAN bus.
Unit Behavior
Shutdown and alarm.
Reset Conditions
Auto reset when CAN communication is restored, alarm reset or alarm may be manually reset by turning the unit off, then back on again.
Corrective Actions
1. Check Both Active and Inactive Alarms for other “NO COMM” Alarms a. If more than one alarm, record all and proceed to step 2. b. If this is the only alarm, check for continuity: CAN Hi: 1MM-2 through SP-1 to ENCU-23. CAN Lo: 1MM-4 through SP-4, to ENCU-24. c. Replace ENCU. 2. Check CAN Bus a. Inspect connector pins and terminals on 1MM and1SVM. No damaged or corrosion in connections. b. Check for CAN continuity: CAN Hi: 1MM-2 through SP-1 to ENCU-23. CAN Lo: 1MM-4 through SP-4, to ENCU-24. If good continuity is not present, check connectors and wiring between terminals for damage, moisture or corrosion. 3. Check System: Clear active and inactive alarms. Start unit and monitor for additional “NO COMM” alarms.