Okay guys, check this out and tell me what you think...I pulled this off of another website..."The Calpak is that other, smaller, chip next to the eprom. The dealer has them. It contains part of the fuel control code.
1987 Chevy S-10 Blazer with 2.8L PART GM# 16051459
Trouble Code 52 indicates that the ECM sensed a fault with the CALPACK. The CALPACK is a plug-in module separate from the PROM, that contains preset calibrations used by the system during "limp home" (backup) mode. The ECM continuously checks for its presence while power is applied.
The conditions for setting this code are:
the ECM does not sense the CALPACK
Typical causes for this code include:
1) Incorrectly installed CALPACK module
2) Incorrect CALPACK module for this vehicle
3) Defective or incorrectly inserted PROM
4) Defective ECM
5) Missing, as in swapping computers and swapping the eprom but forgetting to swap calpak also!
When I got the re-manufactured ecm from NAPA...I replaced the PROM but they said nothing about a CALPAK!