1997 Western Star log truck cat 3406e

Check the engine harness where it runs by the A/C compressor, it has been known to rub there. I've repaired 2 other WS w/ E models with the same problem and found the harness rubbed at that point causing a intermittent short.

 

Also check the same engine harness where it goes into the valve cover riser plug in.
Also the engine should have good ground, usually a ground wire from the starter ground going up just above the ecm.

Ecm is very sensitive and you don't want to run a higher fuse. I'd recommend changing it back to 15 amp. and finding the problem.

 

No question its wiring. Its time to spend a lot of quality time with your wiring harness.

 

Why not just put an new engine wiring harness on considering how cheap they are. I was surprised to find this out on my 99' 3406e. I went right to Caterpillar and picked one up for under $300.
If you do change it out, be sure to mark or make note where each plug in goes since they are identical plugs and will interchange on the sensors.

 

I just had problems on a 97 star with a 3406e recently. Issue ended up being a bad ground wire on the stud in the head behind the intake

 

There is a wiring schematic docked in the garage section thread. Actually I think it's a link to a web site with a PDF schematic.