There also is info about the code 2-1-2 (O2 sensor) in the faq, including this tidbit:

"Code 2-1-2 "Faulty Oxygen Sensor" in 960 Cars. [Rafael Riverol] If the check engine light on the dashboard lights up and you read OBD I diagnostic code 2 1 2 (faulty oxygen sensor (O2) signal) in your 960, undo the red and blue four way O2 connector near the oil dipstick and check inside. The metal spades in the male connector are surrounded by silicone like material which crumbles, particularly after you apply electronic connection cleaner or the like. The particles can fall within the male and female connection, even inside the female connector contacts, and cause a faulty O2 sensor signal. Take out the loose material with sharp tweezers. Make sure all contacts are clean and undistorted and connect back together WITHOUT using silicone dielectric grease because of low signal voltages. Clear the codes. This procedure should eliminate the faulty signal."

FWIW, I replaced the O2 sensor and cleaned the connectors, but still am getting the code 2-1-2. A post from another reader indicated that he had the same condition, and even after replacing the O2 sensor he continued to have the code. It didn't clear up for him until he replaced the power stage amplifier. I guess the lesson is that several things can cause the code 2-1-2, so I wouldn't replace it without having it checked. May be something else.