My neighbor's little rat terrier showed an active interest in my car out in the driveway.
I opened the hood on my 1999 323is and found that a rat had chewed the hood insulation and tried to make a nest by the new secondary air pump.
Nothing else looked like it had been chewed or damaged, so I washed out the nest and took it for a ride. The check engine light came on as well as the transmission warning
symbol. I stopped, let it sit, and started it again. The tranny light came on as it
shifted from 2nd to 3rd and it wouldn't downshift as the speed diminished.
The check engine light was OBDII code 0720 (Output Speed Sensor Circuit). I went under
and over the engine and drive train. I could only find the wires to the cooling sensor and nearby alarm horn had been chewed off. I replaced them and reset the OBD code.
It was fine for a block or so, then both warning lights came back on. I can't find any
other chewed wires.