Suspect immobiliser
 

Hi everyone, first-time post.
I have a 2003 b2500 double cab. It works hard and has given me many years of relatively hassle free service.
About a week ago I tried to start it. Turned the key - all lights came on
Inserted the fob key to deactivate immobiliser - heard a click BUT the preheat coil light did not come on
Puzzled I turned the key - cranking but not starting.
I randomly checked and cleaned the connections on a bunch of fuses but was then late and took my wife's car.
That afternoon I tried to start again - No Problem! Yay.

Two days later after many stops and starts and many kilometres same thing happened. Random fiddling and a couple of tries and term mins later I was on my way.

Then two days ago I got to a client, stopped the truck and was asked to move as I was blocking the drive for a delivery. No coil light and no start.
I spent the entire afternoon trying everything I'd done before but eventually had to get a lift home. Yesterday I went back, got in and it started like nothing had happened.
I drove home but when I tried to leave again later - same story.

​​​​​i was told by a mechanic friend of mine over the phone that it is possible to bypass the immobiliser.
I understand the security implications so I was wondering if any of you have successfully done this perhaps you could PM me a solution or a diagram. Electrical things are not my forte and I'd really love a tried and tested diagram rather than risk shorting out or blowing up anything important.
Thanks in advance

I would be looking at the glow plug relay, seen a few go bad over the years.

Theoretically it may be possible to bypass the immobiliser, however, the immobilizer prevents cranking the engine from memory.