It sounds like the gear range sensor has come apart internally and needs replacement. Here is the correct way to replace the sensor so the repair can be successful.
The diagnostic trouble code P1705 for your 2016 Ford Transit indicates an issue with the Transmission Range Sensor (TRS), specifically that it is "Out of Self-Test Range."
I would consider getting used unit from ebay. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.
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Sunday, November 10th, 2024 AT 5:57 PM