Hobart L30 show code P3 and tempreture rises high Very quickly before it finsh filling

P3 refers to one of the dishwasher's three temperature sensors: sump temperature, booster heater temperature, or rinse water temperature. The dishwashers control circuitry has determined one of them is open or shorted, or at least out of range.

Judging from the symptom you mentioned, that you see rapid temperature reading changes before it finishes filling, I'd say it's probably the sump probe (because that's the temperature displayed during the fill cycle), located under the large removeable screen inside the dishwasher.

To test or replace, remove the small access panel at the lower front of the dishwasher (2 screws).
After the dishwasher has reached a good normal operating temperature, unplug the sump probe connector (white plastic connector with two small black wires going to it and coming from the area mentioned above where the temp. probe is. Using a multimeter, test the resistance of the probe. If the water in the dishwasher is hot (150 deg. F or more), you should read somewhere in the area of 5,000 to 10,000 ohms. If your measurement varies significantly from this range, replace the probe- most likely you'll see a reading near zero ohms or a very high reading, possibly an open-circuit probe (infinite resistance i.e. "OL" indicated on most multimeters).

It's possible I'm wrong about which temp. probe P3 refers to. There is also a temp. probe on the booster heater and one on the rinse piping on the rear of the dishwasher. Test procedure is the same for all of them, although the probe on the rinse piping is not constantly subjected to hot water so testing at room temperature would result in higher resistance value (lower temperature means higher resistance for these temperature probes).