No Comm from Micro to STP1
refrigeration
Description
The main microprocessor cannot communicate with the stepper valve module over the CAN bus, and the unit shuts down and alarms.
Activation Conditions
If alarm 21100 No Comm from Any Board to Main Micro is not active and main microprocessor cannot communicate with stepper valve module over the CAN bus.
Unit Behavior
Engine and Electric Operation: Shut down and alarm. The stepper valve module status LED may be on steady green (not pulsing) or red.
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 3. b. If this is the only “NO COMM” alarm, replace module. 2. Check status indicator. Refer to Section 2.5.4 3. Check CAN bus a. Inspect connector pins and terminals on 1MM and 1SVM. No damaged or corrosion in connections. b. Check for CAN circuit continuity: CAN Hi; Refer to Section 4.2 CAN Lo; Refer to Section 4.2 If good continuity is not present, check connectors and wiring between terminals for damage, moisture or corrosion. Repair if required. 4. Check system - Clear active and inactive alarms. Start unit and monitor for additional “NO COMM” alarms.