Whirlpool ADP4601 2 Flashes

Hi,

I have a Whirlpool ADP4601 dishwasher which has not been used for some time. The landlord say its new and has never been used. When we tried running the cleaning cycle, that ended with 2 flashes and half empty cleaning liquid. We re-ran the cycle but same result.

Looked it up on internet and error means there is leakage somewhere. My question is how do I locate the leakage if the door needs to be closed to run the cycle?

Thanks