Sorry, I don't know either, but I've been living with this error code (and code 5
on my '92 SSE */c since I bought it in 1999. If anyone finds a fix for this, I'd like to know.
I recently asked a tranny shop owner about this error code, and he said not to worry about it because there are other mechanisms to tell the tranny what gear it'* in, and the PRNDL switch is expensive to replace.
After I talked with him, I looked at the switch and found that the mounting bolts were just a little loose. I cleared the error code and tightened the bolts and haven't had that error code since then. It'* been several weeks now, but I'd be surprised if the bolts were the cause of the error because although they were a little loose, there wasn't much clearance. The switch is mounted on the top of the tranny, driver'* side, where the linkage mounts to the top of the tranny also. It doesn't look like a 'switch' to me; it'* kinda odd looking.