After uploading some new settings last night, I turned off the car and locked it, forgetting to unplug the IID tool.

This morning- car as flat as a fart. Wouldn’t even unlock with the remote.

Just how much current draw does the IID tool take? 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded

This could be an early warning of a looming battery problem, I had mine plugged in for a couple of weeks while trying to capture data for an intermitant fault and didn't have a problem.
Could you have partly flatened your battery when you were making your changes?

IID manual states an external power source should be connected when CCF editing etc.
Most folks use a Ctek with 12V supply mode  Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
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I didn’t know this.

There’s a Manual? 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded

CCF editing / module programming draws a lot of current and you should have a stable, external supply connected. Another option is to connect to another running vehicle via jump leads. I'm not sure that's recommended though...

The manual is on the GAP website. 2016 Skoda Octavia VRS Estate
<gone>2009 FF Vogue TDV8 Buckingham Blue</gone>
<gone>2015 BMW 520D SE (not my favourite car)</gone>
<gone>2009 D3 HSE Galway Green</gone>

Learnt this pretty early on the D4, the problem isn’t how much the IID tool draws its the fact your car doesn’t go to sleep that’s the issue.

Download manual on IID website. It's not the easiest to negotiate but give it some time Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
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The IIDTool draws charge when the ignition is off.

If you are using the IIDTool regularly an extension lead with a switch as below is highly recommended. The pins in your OBD port on your car will gradually get knackered if you continually plug the IIDTool in and out, and replacing them is a big job according to LR (they prefer to re-loom rather than cut and solder).

https://www.amazon.co.uk/gp/product/B073Y2...&psc=1

I had to get the RAC out to start the car. It was on 7 volts when he connected his jump leads. It took his boost pack and his van to get it started.
Bizarrely he said the battery was ok. Halfords also said the same. I’m still not convinced it is healthy. 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded

Andy,
send Patrick at GAP tim email and ask for advice. I keep mine plugged all the time without any problem. mine is BT tool 2012 TDV8 Black Edition
2000 Disco. TD5
1975 series III

Page 56 of the manual might help? Pretty sure Pat at GAP will advise the same.

Click image to enlarge

I don’t leave it permanently connected. This was accidental. 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded