1993 Lexus GS 300 Code 12

This code means there is a fault in one of the camshaft sensors or the crankshaft position sensor. The signal is either open or shorted to ground. The camshaft position sensors are located underneath the timing covers on each bank. The crankshaft position sensor is located under the cover on the bottom of the engine towards the passenger side front. The resistance of the sensors should be about 850 ohms to 1400 ohms cold. If the timing belt was done recently make sure the wires did not get unclipped and rub through on the timing belt for the cam sensors.