I replaced the head gasket because the old one leaked oil (typical for this engine at about 100K). I think that 1996 was the first ODBII year and the wiring scheme changed from 1995 when this engine was used in, for example, the 124 chassis series. I have the W124 CD and my wiring looks nothing like that illustrated in the CD. I agree that a position sensor or ECT sensor (or its wiring) is a likely culprit. I want to test the signals from these sensors by backprobing at the PCM connector to verify that good data is actually getting to the computer.