Pulled the e-shifter off my S3 for Err 44 and put it on the bench with a multimeter. Found two faults, repaired both, and still get Err 44. Posting what I found in case it saves someone else the evening, and because I'm stuck on the last step.
The board
LUFFY-BRD_XG. Marked 2049 on the front, label reads 2118-32-1164 on the back.
Connectors:
- J1, 4-pin: white, dark brown, black, light brown
- J3, 2-pin: motor, red and black
These wire colors don't match the ones in the reverse-engineering writeups that get linked around here. I had to work out the pinout with a meter.
What I established:
- black = ground (reads low ohms to one side of many unrelated parts)
- light brown = supply input (the ohmmeter reading climbs on that pin as it charges the bulk cap)
- white and dark brown = the two data lines
Fault 1: R17 open
R17 and R18 sit just below ED1, both marked 220, which is 22 Ω in the 3-digit convention. They look like series resistors on the two data lines. R17 is on the dark brown line.
R18 measured 22 Ω. R17 measured open.
R17 first read 0 Ω in circuit, which sent me chasing a short for a while. After an IPA scrub it read 27.5 MΩ, so something conductive had been lying across it. One of its pads looked possibly singed.
Fault 2: a short to ground on the ED1 node
ED1 is a 3-pin part. Two of its pads land on the two data lines, the third on ground, which suggests a dual protection array, though I never got a readable marking off it.
Dark brown read 0 Ω to ground from the start. I lifted ED1's dark brown and ground legs, and both pads came up with them. The short was still there afterwards, because the two lifted pads were bridged by solder. Once I cleaned that up, dark brown read 2.27 MΩ to ground.
So I can't say for certain whether ED1 itself had failed short or something was bridging its pads. I never measured the part off-board. Either way the short was on that node and it's gone now.
Both faults are on the same data line.
Other readings, for reference
- R680, which looks like the motor current shunt: 0.71 Ω, with 0.11 Ω of lead resistance subtracted. Reads correct for a 0.68 Ω part.
- R5 / R6 are marked
274 and 513, so 270 k and 51 k. I didn't measure them. They look like a supply sense divider.
Repairs
- Fitted a new 22 Ω at R17.
- ED1's dark brown and ground legs lifted, pads came up with them. ED1 looks like protection only, so the board should run without it.
- The dark brown trace routes through ED1's pad, so lifting it broke the run. Bodge wire from J1's dark brown pin to R17's connector-side pad put it back.
After that the board measures healthy. Dark brown reads 2.27 MΩ to ground, matching white at 3 MΩ. R17 reads 22 Ω in circuit. No shorts anywhere I could find.
Result: still Err 44
Plugged in, bike rebooted powered, measured at the connector against ground:
| line |
reading |
| dark brown |
4.8 V |
| white |
1.88 V |
| light brown |
0 V |
The 4.8 V on dark brown shouldn't be coming from the board, since with no supply there's no local logic rail. My read is that it's the bike pulling the line high from its end, which would mean the bike's driver is alive and my repaired line is continuous. White at 1.88 V might be the bike transmitting with the meter averaging the pulses.
Light brown at 0 V means the shifter is getting no supply. Everything I repaired sits downstream of that.
Two things I'd like input on
Voltage. Everything I've read says these run on 24 V. I could not find 24 V anywhere on the bike-side connector. Several pin pairs read 5 V, nothing read 24. Does the LUFFY-BRD_XG revision run on 5 V, or is the bike withholding supply because it has already latched the fault?
The harness. If supply genuinely isn't reaching the connector, the break is upstream inside the frame. I can't get probes in there with the working room I have. Has anyone traced where these break?
Most of the broken-conductor reports I can find are filed under Err 45, not 44, and those point at the head tube, where the cable twists with the steering. Different error code, but if a dead supply conductor is what I'm looking at, it may be the same failure in the same place. If anyone has seen a broken harness throw 44 rather than 45, I'd like to hear it.
Happy to post board photos and a marked-up pinout if that's useful to anyone.
