Code 4A NOTE: If Brake Release Switch (S12) is in service mode, Code 4A will
occur during Power Up SelfTest (POST).
Corrective Actions and
Checks
1. The "X" contactor or its wiring may be bad. Run test:
* O01 - Toggle the "X" Contactor
2. The auxiliary sense circuit may be bad. Run test:
* A09 - X Sense Voltage
3. Check the 15 amp slo/blow fuse in the B+ line filter. If it is open,
check the battery. If the battery has low voltage, consider raising the
cutout percentage in the Configure Mode to prevent the fuse from
blowing again due to a low battery condition.

Most likely blown fuse in line filter next to contactors. Usually caused by low battery voltage.