Sourcing a YT Decoy harness is genuinely one of the more painful jobs in eMTB ownership right now, so let me be straight with you about where things stand.
Your Decoy MX runs the
Shimano EP801 (85Nm, 600W), so the main motor wiring is Shimano's system — which is both good and bad news.
The honest state of play:
• YT-specific harnesses have been a known weak spot.
@T4RZAN reported that during the YT insolvency mess, Shimano was pointing the finger at the YT harness as the fault, but
no aftermarket wiring harnesses were available for the Decoy — it's a YT proprietary loom, not an off-the-shelf Shimano part
→ view post.
•
@ziscwg confirmed YT USA is now handled through
Jenson USA — they still warranty YT bikes, but you contact Jenson first and they liaise with YT
→ view post.
Where to actually look:
•
YT direct / your regional YT service — for a UK bike, go through YT's own warranty/spares channel first. The full main harness is a YT part number, so they're the primary source.
•
Jenson USA if you're Stateside — same caveat, contact them before buying.
•
Shimano service centre — worth a call, because some of the connector-side bits (drive unit cables, the Z405-type light/accessory leads) are standard Shimano EP8 parts even if the full loom isn't. If only one branch of the harness is faulty, you may not need the whole thing.
Before you spend on a full harness — diagnose first:
Harness faults on these are very often
corrosion at a connector, not a dead loom.
@SVT_925 traced an intermittent on/off Decoy fault to corrosion in the main harness and sorted it for around $30 in parts
→ view post. Worth pulling each connector, checking for green crud and water ingress, and cleaning/re-seating before you write off the whole thing — eMTB harnesses are notorious for water creeping in and backdooring into connectors.
If you can tell me the exact symptom (no power, intermittent cut-outs, error code on the display, or a specific cable that's visibly damaged), I can help you work out whether it's a single cable or the full loom — and that changes the cost massively.
What's it actually doing?