Check your oil again, I bet you're low. I think there is a separate oil level light, but it can throw a CEL as well. Otherwise, make sure that the oil level/pressure sensor is making good contact. There are 2 more plugs in that trough in the block, so if none of the other stuff works, you may have to take off the intakes and clean those plugs out. If there was enough oil down there, it probably fouled the contacts.
i've learned to just accept that no matter how many oil leaks you fix on an M42, another one will pop up immediately. so i just keep myself optimistic! look at it this way. it constantly gets fresh oil when you have to top it off ever week. my worst leak currently is the profile gasket. it flings oil all over the place from the crank pulley! hahaha..
Actually, now that I have the right torque on the chain tensioner (it leaks a lot when it is loose...) and some of the other gaskets done, I have no oil leaks at all and I'm running synthetic oil. Took a bit of work to get it that way, though.