You can use a small piece of wire or a paper clip would work too. A code 12 will start and that is normal. 15 Coolant sensor or circuit fault - LOW temperature indicated. Signal voltage is high during engine idle or deceleration.
Signal voltage is low during engine idle.
Open or short circuit problems. Signal Circuit Error - possible faulty crankshaft position sensor or circuit. 37 Brake switch stuck on. 41 Cylinder select error. 53 Alternator voltage out of range.