Replacing an e-bike bottom bracket torque sensor is a specialized task that requires the right tools and expertise. Here's a step-by-step guide on how to go about it:

Safety Gear Needed:

• Safety Glasses
• Work Gloves

Tools Required:

• 8 mm Allen Key
• Crank Puller
• Bottom Bracket Tool
• ISIS Splined Bottom Bracket Removal Tool

Step-by-Step Guide

Preparation:

1. Disconnect the Battery: Make sure your e-bike’s battery is disconnected for safety.

2. Loosen the Chain: Free the chain from the chainring to make your workspace clear. ( Tip: Carefully push the rear derailleur arm forward, towards the front of the bike. This will create slack in the chain)

Removing Old Torque Sensor:

Step 1: Take Off Crank Arms

• Use an 8 mm Allen key to loosen and remove the bolts holding the crank arms.
• Use a Crank Puller if the arms are hard to remove. 

Step 2: Remove the Chainring Nut

• This is a tricky step. Use the ISIS Splined Bottom Bracket Removal Tool and turn it clockwise to remove the nut.

Step 3: Disconnect Old Sensor

• Trace the wire from the old sensor to where it connects with the e-bike’s controller. Gently disconnect it.

Step 4: Remove the Old Bottom Bracket

• Use the Bottom Bracket Tool to turn clockwise and remove the bracket on the right side.
• Use the Bottom Bracket Tool to turn counterclockwise to remove the nut on the left side.

Installing New Torque Sensor:

Step 1: Prepare New Sensor

• Apply grease to the threads of the new torque sensor.

Step 2: Install New Sensor

• Use the Bottom Bracket Tool to screw the new sensor nut clockwise on the left side. Torque it to 35 Nm.

• You'll need to simultaneously insert the torque sensor into the bottom bracket opening while threading the cable through the top hole. On the other side of this hole, you'll find the controller. Since the cable length is limited, holding the connector might be challenging. If needed, use tweezers for better control. Use the Bottom Bracket Tool to screw the new bottom bracket counterclockwise on the right side. Torque it to 35 Nm. (Caution: Avoid crushing or forcing the cable, as this can cause damage. If you encounter difficulty during installation, remove the sensor and try inserting it again for a smoother process.)

Step 3: Connect New Sensor

• Route the wire from the new sensor to the e-bike’s controller and connect it.

Step 4: Reassemble Bike

• Place the chainring back and install its nut counterclockwise using the ISIS Splined Bottom Bracket Removal Tool. Torque it to 35 Nm.

• Reattach the crank arms and use an 8 mm Allen key to install the crank arm bolt. Torque it to 38-42 Nm.

• Reinstall Chain: Put the chain back onto the chainring.

Final Steps:

1. Test Bike: Reconnect the battery and test to ensure everything is working well.

Note: If you're not confident in doing this on your own, please consult a qualified technician for assistance.

I hope this guide is clear and easy to follow. Good luck with your task!