Will Curt Wiring Harness Set Off Check Engine Light on a 2018 Ford Transit
Updated 01/12/2026 | Published 09/02/2024
Question:
Installed curt trailer harness in 2018 ford transit. All lights working fine but check engine light is now on. Any ideas? Thanks
asked by: Joseph G
Expert Reply:
Hey Joseph, thanks for reaching out!
The Curt T-Connector Vehicle Wiring Harness # C56327 that you purchased for your 2018 Ford Transit (thank you for that by the way) shouldn't be throwing a check engine light because it only tees in behind the tail lights and pulls power straight from your battery. What I recommend doing to verify this is to disconnect the tee-in connectors behind your tail lights and plug the lights directly into your OEM plug - if you still have the check engine light then you know you need to take your vehicle to get the light checked.
Product Page this Question was Asked From
Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- Powered Converter
- No Tow Package
- 4 Flat
- Plug and Lead
- Plug-In
- Hidden
- CURT
more information >
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Jesse M.
1/12/2026
Hey Joseph, did unplugging the Curt trailer harness and reconnecting your Transit’s lights clear the check engine light? Knowing what happened could really help others who run into the same issue after wiring their harness.