L4-70 Toner Motor Lock Trouble MX-M266N

[yurisan]

Here's a strange one that's got me confounded -
Deliver & install a MX-M266N w/ only 13K. 2 days later (and several hundred pages of printing) customer calls w/ L4-70 trouble (toner motor lock trouble).
Go there w/ toner motor/drive assembly and PCU PWB off a similar, low meter (23K) MX-M266N that we have. I'm thinking it's 50/50, PCU vs. motor, so I swap out the PCU first (swapping eeproms to maintain settings) because removing the toner motor assy is a bit of a pain because of the crazy wiring harness it incorporates. Voila' it works, the copier is once again replenishing toner - all is well. Next day (and several hundred more prints) the customer calls w/ L4-70. So, now I can assume the motor/toner drive assembly is bad.
I had previously put the customer's PCU in our MX-M266N in the shop and it turned toner motor from that machine (I only changed customer's PCU, not both PCU & motor). So, I know customer's PCU was good all along. I take shop motor to customer, install it and it DOESN'T WORK. The toner cartridge is new and spins freely, by the way, but I have another new toner and try it - just because....... and get same L4-70. I have been careful in transporting these components to and fro, by the way. I get back to the shop and now the customer's toner motor doesn't turn in Sim 10-1, whereas mere hours ago, the motor original to the shop machine which now has the customer's PCU was turning fine in the Sim mode.
So, it's NOT a case of the motor taking out the PCU, because the customer's PCU operated correctly in our shop machine. At this point, I've got the shop PCU & motor combo in the customer's copier and customer's combo in the shop copier, also not functioning. Perhaps, they have both caught the coronavirus.

[Prints Charming]

The Toner Motor manufactured prior to October 2016 was known to blow a fuse on the MCU PWB, and subsequently shown L4-70.
The new toner motor part number is DUNT-1220RS56 (was DUNT-1220RS52).

You need to replace the MCU PWB and the new toner motor.