No Start (sometimes).

Hi, my '03 K12 starts and runs beautifully, except sometimes:
Starts fine, but cuts out after a few hundred yards, will re-start fine after a few mins.
Recently, if turned off refuses to start for a while.
Thinking dirt in pump, tank was 1/4 full, so put more in started then.
No check engine lights.
No chain noise on cold start.
Cranks fine, just no start.
OBD faults with my cheepo and garage proper scanner too:
P0340 camshaft sensor (sometimes)
P0138 o2 sensor circuit
P0037 ho2s heater control
My trustworthy mechanic says come back for scan after faults occurs again.
He thinks it could be immobiliser, try key out, lock and unlock to reset,
Does iffy immobiliser allow cranking, but no starting?
Thanks for any suggestions!
You didn't say what fuel your car runs on? my Micra is diesel, however my two suzuki's which do run on petrol have started doing the same, ok if you start them and then set off and come to a juntion and they cut out, my cars run perfect so it is without doubt the crap petrol that is been passed off as fuel (10% ethenol) with plans to increase in the US to 15%!!!, If your car is petrol try the super unleaded which is still 5% ethenol OR add a petrol additive to help the engine burn it more effeciently i.e benzin additive, and see how you get on.:unsure:
Thanks for the reply, my car is a 1.0 Litre petrol. Here in Ireland petrol is still 5% Ethanol (Hmmm, the same as good beer). There is talk of moving to 10% soon. I will try an additive or better fuel.
Anyone else?
Thanks for the reply. Mine's one of the first, so it could be the chain, but I hear no undue noise at a cold start, and no check engine light. I might have to pay someone to look at the chain, but I'm not sure the car warrants the cost of replacement. It's a fun drive, though.