GM Code 56

Anyone know what the Code 56 is associated with? I have a 92 PA, replaced most of the sensors, O2, Camshaft and Crankshaft sensors. New code that I am getting is a Code 56. This does not appear in the 92 PA list of codes, though it does appear in the 93 PA Code List and from what I can tell has something to do with Low Coolant or Quad-Driver "B" (QDM) Fault. Any ideas or help with this?

Al

Did you try resetting the ECM?

Yep, reset it already. Drove to work and once there the error code reappeared. I am going to replace the coolant temp sensing unit and see if that works.

Thanks for the suggestion.