Maintenance icon indicates the metered signals have reached saturation point or the frequency is out of range.
Refer following Error Bitmap register 4112 for more details;

Error Bitmap:

bit 0: Phase A Voltage out of range

bit 1: Phase B Voltage out of range

bit 2: Phase C Voltage out of range

bit 3: Phase A Current out of range

bit 4: Phase B Current out of range

bit 5: Phase C Current out of range

bit 6: Frequency out of range or insufficient voltage on Phase A to determine frequency

For example: it is normal when the register 4112 = 00000000

If there is any bit =1, then a WRENCH icon (Maintenance icon) will be illuminated on the front display of PM7 meter.

For example: Bit 3 is linked to current, which measures from 5 mA to 6 A; if it is outside this range (i.e. without load or overload), bit 3 =1;