Checked the wire & connectors under the fuel pump first. All seemed ok, or at least the engine light didn't come on when I was jiggling them.

Next looked for & found (I think) the tacho sensor wire. Whether this was the cause or not - it needed attention. It's connector - higher up on the top left front of the motor - had broken off it's steel mounting plate, the able had also come out of a cable holder bolted to the motor & was obviously able to flop around quite a lot. The corrugated plastic conduit around the cable had obviously made contact with the fan blade & was torn. Amazingly though the cable itself appeared undamaged. Connector re-mounted with cable ties & measures taken to ensure the cable can't get close to the fan blades again, or onto the belts below it. I held the fan blades whilst MrsTea started the motor (I knew I could, but still scary) & then jiggled the cable, sensor rubber cover & connector (with a length of stick - not putting my hands down there whilst belts are moving in close proximity!). Still no engine light coming on.

Couldn't find the ambient temp sensor, but didn't look too hard as the ambient temp was in the 'bloody hot' category out in the full sun.

Will now wait until we drive on corrugations again to see if the engine light coming on as been sorted.

BTW I thought the denomination for the factory intercooled TD42's was TD42i ..... Not TD42Ti I'll look for the ambient air temp sensor if the engine light is still coming on .......& when we have a shadier spot to park up.

Supplementary question 1: What light illuminates on the dash if the fuel filter gets enough water in it?

Supplementary question 2: I have had issues with a few of Nissan's plastic cable connectors either breaking or being seized closed over the past couple of years, they are buggers especially when difficult to reach & often appear unneccesarily complex. At 13 years old they seem to be getting toward the end of their life. Can they be bought & if so are there model numbers for them? Or what are the best aftermarket connectors to replace them with, given that many are supposed to be waterproof. A couple I couldn't get apart I just cut off & replaced with spade terminals + tape, but it might be good to carry a few waterproof multi pin connectors as well?