1995 S-10 Code 41 Please help

I'm getting a trouble code 41 on a '95 S-10. The Haynes book identifies it as: "IX Signal Error". The chilton identifies it as: "Cylinder select error -MEM-Cal or ECM problem. I have replaced the ECM and the code cleared. I ran the truck for a minute and checked for trouble codes again and it's giving me code 41 again. I can't find any info about this code or the procedure for fixing the problem. Please help.

check the crankshaft sensor or the camshaft sensor or both. the code 41 appears to mean it cant see a cylinder id reference signal.

yip, what he said.