Sc990 during firmware update

[Ltd]

AF2045esp start having a red wrench during I do update Engine and system firmwares. The new firmware are in machine. Turn on machine, after "Please wait" SC.990 pop up right away, No motor turning. What I did :
- Swapped whole completed new set of controller unit from a good machine to this machine,Code still show even I did not close the doors yet.
- Cleaned all door SW(not dirty), completed major PM, Cleaned ID sensor.
- HDD disconnected , Ram, Nic removed still same code.
Where are the firmware stored when you update them ?

Before this happen, Machine run normal, cleaned.

[TonerMunkeh]

990 is usually caused by a duff drum. Service the PCU and try again.

[Ltd]

990 is usually caused by a duff drum. Service the PCU and try again.

Brand new PM, cannot make any copy out of it due to stuck SC code.

[TonerMunkeh]

When this SC occurs, the file name, address, and data will be stored in NVRAM. This information can be checked by using SP7-403. Note the
above data and the situation in which this SC occurs.

Depending on what filename it comes up with it'll point me in a certain direction. Have a look, post back on here and I'll do some more digging.

[Ltd]

Replaced BICU

I replaced BICU, SC990 gone. I just shocked and did not think BICU is the cause. Just a little information for the group references in the feature.