Bobby
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If you’ve replaced your door speakers or removed your door trim and noticed that your window drops a little more each time you open or close the door, you’re not imagining things — and you’re definitely not the first Z owner to run into it.
Fortunately, the fix was simple once I knew what was happening.
Why I think It Happens:
The Nissan Z uses frameless doors with automatic window indexing. When you open the door, the glass drops about 10 mm to clear the seal; when you close it, it rises back up for a tight fit. This behaviour is controlled by a small computer built into the window motor, which memorises the exact upper and lower limits of the glass.
If you remove the door trim while the battery is still connected and unplug the window switch harness, the window control module can lose its calibration data. The Body Control Module (BCM) and window motor then get out of sync. Each time the door opens or closes, the car thinks the window isn’t in the right position and lowers it slightly more, causing the glass to “walk down” over multiple cycles.
The Fix that Worked for Me:
I didn't need any special tools or dealer software — just a battery socket and a few minutes.
1. Disconnect the negative battery terminal
Leave it disconnected for at least 30 minutes.
This fully clears the memory in both the BCM and the window motor.
2. Reconnect the battery and turn the ignition ON (engine off is fine).
Make sure the affected door is fully closed.
3. Perform the window recalibration:
Lower the window completely using the switch. Hold the switch down for 5 seconds after it reaches the bottom.
Raise the window completely. Hold the switch up for 5 seconds after it reaches the top.
Repeat the up/down cycle once more for good measure.
4. Turn the ignition OFF, wait a few seconds, then turn it ON again.
Open and close the door a few times — the window should now drop and raise normally (about 10 mm each way).
That’s it — your window indexing is now restored.
How I think I could have prevented it:
When doing speaker upgrades, sound deadening, or other door work:
Always disconnect the battery before unplugging the window switch or any other door wiring.
Don’t cycle the ignition while a door harness is unplugged.
After reassembly, run the 5-second up/down calibration before closing the door.
Following these steps avoids losing the calibration in the first place.
Good luck
Fortunately, the fix was simple once I knew what was happening.
Why I think It Happens:
The Nissan Z uses frameless doors with automatic window indexing. When you open the door, the glass drops about 10 mm to clear the seal; when you close it, it rises back up for a tight fit. This behaviour is controlled by a small computer built into the window motor, which memorises the exact upper and lower limits of the glass.
If you remove the door trim while the battery is still connected and unplug the window switch harness, the window control module can lose its calibration data. The Body Control Module (BCM) and window motor then get out of sync. Each time the door opens or closes, the car thinks the window isn’t in the right position and lowers it slightly more, causing the glass to “walk down” over multiple cycles.
The Fix that Worked for Me:
I didn't need any special tools or dealer software — just a battery socket and a few minutes.
1. Disconnect the negative battery terminal
Leave it disconnected for at least 30 minutes.
This fully clears the memory in both the BCM and the window motor.
2. Reconnect the battery and turn the ignition ON (engine off is fine).
Make sure the affected door is fully closed.
3. Perform the window recalibration:
Lower the window completely using the switch. Hold the switch down for 5 seconds after it reaches the bottom.
Raise the window completely. Hold the switch up for 5 seconds after it reaches the top.
Repeat the up/down cycle once more for good measure.
4. Turn the ignition OFF, wait a few seconds, then turn it ON again.
Open and close the door a few times — the window should now drop and raise normally (about 10 mm each way).
That’s it — your window indexing is now restored.
How I think I could have prevented it:
When doing speaker upgrades, sound deadening, or other door work:
Always disconnect the battery before unplugging the window switch or any other door wiring.
Don’t cycle the ignition while a door harness is unplugged.
After reassembly, run the 5-second up/down calibration before closing the door.
Following these steps avoids losing the calibration in the first place.
Good luck
