Immobilizer causes problems

Moin, we have the problem that the previous owner of our 850 2.5 petrol engine said smart as he is to retrofit an immobilizer himself and since then the car has repeatedly the problem that after starting some lights in the speedometer do not work and also light, turn signal ect. does not go. Now the car has such a small box with a small socket key. Now my question: Can you possibly bridge the immobilizer that you no longer need the key for it?