Many a fine battle-hardened appliance warrior has been befuddled by these error codes and have needlessly soiled their undergarments throwing every control board in the box at it.
But these serial communications error codes all have one big thing in common:
They are almost NEVER caused by a bad circuit board! Instead, they are exactly as the error code description says: a COMMUNICATIONS error between two boards. In other words, a bad connection.
Oh, I know— you’ll hear some guys swear it was a bad board because they replaced the such-and-such board and it fixed the problem, so it had to be a bad board. But I’m here to show you that in 99.9999% of these cases, the board itself is perfectly functional but the real problem is the CONNECTIONS to the board.
“Uhh, howzzat, Samurai Smart-ass Guy?”
Ahh, Grasshoppah, make still your mind and the Samurai shall reveal the truth unto thee. And the truth shall make you free. Come with me now on a journey of Total Appliance Enlightenment™…
Let's think about the modern front loading washer and the average laundry room for a minute. In these front loaders, you have at least two (CCU and MCU) sometimes four (CCU, MCU, UI, and Steam Board) different boards that all need to talk to each other and pass data back and forth: digital data, voltages. How do they do this?
Since they haven’t incorporated internal Wi-Fi into appliances yet, all these boards are connected to each other by special wire harnesses called serial communications cables. All this data exchange is fact-checked and verified by a process called “handshaking” (yes, that’s what it’s really called). If, at any time during this continuous process of passing data back and forth an error is discovered during the handshaking, the CCU throws a serial communications error. The closest it can get in the error code is by telling you which two boards had trouble talking. But that’s close enough!
So what causes these handshaking errors? Lots of things! In fact, given the conditions that these washing machines have to work in— lots of vibration, moisture, humidity, heat, etc.— it’s amazing they work as well as they do. But all it takes is a loose connection at a molex connector on a wire harness or an oxidized pad on the control board to disrupt that handshaking. It doesn’t even need to be a totally broken connection, just one with low enough signal-to-noise ratio that the CCU can’t tell which is signal and which is noise.
Okay, here’s the part you’ve been waiting for: the Silver Bullet Fix for these elusive and mysterious serial communications errors in Whirlpool-built front-load washers.
The harness itself can (and usually does) check good. That's not usually the problem. The problem is at the harness connection points where the molex connector on the harness connects to the boards at either end. The tines can become loose or the pads on the board may become oxidized. Here's a technique that I've used with great success in these types of problems. BTW, all modern front loaders work the same way and use pretty much the same basic technology so this solution concept for serial communications errors applies to all brands of front load washers, not just Whirlpool: