NATS Signal Wire Strangeness

Hi all, I'm putting a CG13 in my mini, and I'm having a bit of an issue getting it to start. The engine is from a 1999 micra, with NATS 5? I think, with 7 wires. I've had the engine running before, but since then I pulled it out to tidy everything up, before putting it back in. Fuel is circulating through the rail, there's spark, and its cranking nicely. the plugs are dry, so I'm assuming the ECU isn't firing the injectors. I've been following the NATS issue troubleshooter guide in the workshop manual, and I think I may have found the issue, with the ignition on, I get about 7V between the NATS signal wire and ground, where the manual says there should be nothing, I've chased the wire through, and the issue seems to only be present when the ECU is present, which to me implies the ECU is acting oddly.

If anyone has any ideas on what might be causing this, or what might fix it, I'd really appreciate the help!!

You'll probably know more about this than me if you're chasing wires and testing on that level, auto-electrics isn't my strong point

I've been doing a ton of troubleshooting with ECU's though, if you can connect up the original micra dashboard and tell me what lights show up when you're cranking it then you could potentially figure out if it is NATS interference or some other issue. Also the colour of the chip inside your key is relevant. I think red chip is NATS 5.

There is also a light on the ECU itself, I can't say which side it's on because they seem to have put the housing on different every time they built one. But if you pull it out and shine a torch in there you can see the red LED inside vs just a regular screwhole. The red LED inside the ECU flashes the same way as the malfunction indication lamp/check engine light on the dash. There is also an LED on the dashboard that is supposed to act as a theft deterrent that shows whether the alarm is active that behaves slightly differently

All operating correctly: the LED on the dashboard should be flashing all the time with or without the key in as long as the battery is connected. When the key is turned to "on" but the dashboard LED goes out, it doesn't do anything interesting during cranking but that is your test that the ECU recognises the key. The ECU light/MIL should light up when the key is at "accs" and "on" as a test that the bulbs are working as should every other light. If you have a tester connected to the OBD port then the MIL shouldn't come on at all. During cranking - the battery light, the airbag light and the handbrake light should all be on, the MIL should go out (as should the light on the ECU) while cranking and then come back on when you stop. If the MIL flashes rapidly or the ECU light flashes rapidly while cranking, then NATS is interfering. There is also a test you can do where you can bridge two of the connectors on the OBD1 port with a paperclip, which will cause both the MIL and the LED on the ECU to flash out a series of codes - if everything with NATS is behaving you could try that and see if there's any fault codes stored in the ECU memory from the failed starting attempts.
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Thanks for the help! The dashboard is long gone I’m afraid, stripped all those wires out, I was able to rig up a light to the nats immu unit though, but it never comes on, tried an LED and a bulb, no position of the key gives anything. Bad sign?
FIXED IT!!! Turns out i had the ignition key wired up wrong, for reference the workshop manual wants pin 4 connected to the on position, not the start position, which is wrong! The Haynes gives the correct diagram, pin 1 to permanent live, 2 for accessories, 3 for on, and both 4 and 5 to the start position. Running really badly and won’t idle, but it’s running!

Thanks again matt