Yamaha PW error 39: Motor phase overcurrent shutdown
The motor controller has measured current above its safe limit on the U or V phase winding. The drive unit cuts motor assistance immediately, so the bike will only pedal unpowered until the fault clears. Walk assist is also disabled while the code is active.
| Drive system | Yamaha PW series (PW-X3, PW-S2, PW-ST, PWseries CE - also Giant SyncDrive) |
| Severity | Dealer needed |
| Keep riding? | Do not keep riding |
| Typical cost | Expect a diagnostic fee around 40 to 80 EUR, a controller replacement roughly 350 to 650 EUR fitted, and a full drive unit assembly 700 to 1200 EUR depending on the PW model. |
Likely causes
- Damaged motor phase cable or chafed harness at the frame exit point
- Corroded or loose connector between motor and controller
- Internal short in the controller board
- Internal winding fault in the drive unit
- Water ingress into the motor or controller housing after a deep water crossing
How to fix Yamaha PW error 39
- Stop riding in a safe place and switch the display off.
- Wait 15 to 30 seconds with the system unpowered.
- Switch the display back on and observe whether the code reappears.
- Inspect the visible motor cable along the chainstay for cuts, pinch marks or crushed sections.
- Unplug and reseat the motor connector at the controller, checking for green corrosion or bent pins.
- If the code clears, test ride at the lowest assist level only.
- If 39 returns, stop use and take the bike to a Yamaha dealer for controller or drive unit replacement.
Warranty: A genuine controller or drive unit failure inside the two year Yamaha frame warranty is normally covered, while water ingress, crash damage and motor modifications are treated as owner fault and excluded.
Typical cost: Expect a diagnostic fee around 40 to 80 EUR, a controller replacement roughly 350 to 650 EUR fitted, and a full drive unit assembly 700 to 1200 EUR depending on the PW model.
Frequently asked
Can I reset yamaha error 39?
Switch the display off, wait around 30 seconds and switch it back on. If 39 is triggered by a transient spike it may clear, but if the controller or motor windings are actually damaged the code will come straight back.
Is it safe to keep riding with error 39?
No, because motor assistance and walk mode are both cut, leaving you pedalling an unpowered bike on any climb, and the controller is reporting an overcurrent that points to a real electrical fault. Stop and restart only to confirm whether the error is permanent.
How much will the repair cost and is it under warranty?
Budget 350 to 1200 EUR fitted depending on whether the controller alone or the full drive unit is replaced. A genuine component failure inside the two year warranty is normally covered by Yamaha, but water damage, crash damage or aftermarket tuning are excluded.
Related Yamaha PW codes
Manuals and video
Official source: cdn2.yamaha-motor.eu
Not an official Yamaha PW document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.