The unit was filled with fluid and taken for a test drive. Upon return, the technician said the transmission was slipping and bucking between shifts. The first thing I did was to look for a check engine light, which was not on (yet). So I went for a test drive. The 1-2 shift was all right, but during the 2-3 shift, engine speed started fluctuating and the check engine light came on. We checked for codes again and found one for an intermittent crank-position circuit. I already had my suspicions as to the problem, but now it was time to prove it with the least possible fuss.