PC Linkage Device
The PC Linkage Device SM-PCE02 is the newer version of the SM-PCE1. Like its older sibling, it can be used to update firmware and customize your Di2 settings. It can also help troubleshoot problems and restore a non-responsive Di2 system. The functionality of this unit is very close to that of the SM-PCE1 - the newer model is said to be faster, a lot smaller and adds a battery check option, allowing you to determine whether any component/unit/bike's power consumption is within reason.
The device has one green LED, one USB port, and one E-tube port. The SM-PCE02 and SM-PCE1 cost about the same, which is still a lot more than the Shimano SM-BCR2 battery charger and that also doubles as a PC-interface. The SM-PCE1 and SM-PCE02 are therefore mainly found at bike shops.
In case you're having a hard time getting your SM-PCE02 to work, I've uploaded the Windows drivers.
Download the zip file, extract it to your hard drive, and then you run the file "ftdibus_(32 or 64)_usbinst.exe". When the installer has completed, run the file "ftdiport_(32 or 64)_usbinst.exe".
Note that you may have to run these files as administrator.
Connect to 12-speed Di2 and EP8 e-bikes
If you're trying to connect your SM-PCE02 to 12-speed Di2 or EP8 powered E-bikes, be aware that these systems use the EW-SD300 wiring standard.
There are two ways to connect the SM-PCE02 to an SD300-type bike.
As of December 2021, you can also use a new SM-PCE02 PC link cable. This is the table that plugs into the SM-PCE02. The other end of the standard SM-PCE02 cable has an SD50 plug. Shimano's new PC link cable has an SD300 plug, allowing you to plug it into 12-speed Di2 components.
The part number for the SM-PCE02 PC Link cable is Y79M9801T.
Troubleshooting and diagnostics
This device does a fair bit more than the regular charger. It has the ability to connect to a single component, instead of only connecting to your entire bike. It also lets you recover crashed components and restore their firmware. However, it will not charge your bike.
Note that the SM-PCE02 should be connected directly to a PC - Shimano recommends you do not use a USB hub.
The process of restoring failed firmware is shown in the video below and there is a page on restoring corrupt firmware on the site as well.