I have a 1990 740 regina. 7000 miles ago I replaced the O2 sensor with the correct regina sensor made by walker. I recently got a 2-3-2 code in socket 2 so I chocked it up to the walker sensor and replaced it with a sensor from ngk (made for regina). Now I get the 2-3-2 code back and in socket 6 a 1-4-3 code (knock sensor signal absent or faulty). I switched the knock sensor with a known good sensor and cleared the codes, but after 100 miles the cel came on and both codes are back. I feel that the O2 and the knock sensors are fine and something else is causing the problem. Car seems to be running fine. Any suggestions? Thanks.