Code 71 on 93 ??

I'm helping a friend with a problem on a 93 Saturn. I got codes 26, 32, 53
and 71. I reset the codes and 53 came right back. I need to know what code
53 is. My scan tool says " INF FLAG - ESC MAX" I can't find it in any of my
service literature.

Al

 

Here's what they all are:

26: Any of the quad-driver module circuits had an open or short for 25
seconds. (Often a problem with either the EGR vacuum or canister purge
solenoids.)
32: EGR system fault. Fuel mixture did not change when EGR solenoid was
commanded ON and OFF. (Points toward possible EGR solenoid problem as well.)
53: Knock sensor could not eliminate engine noise by retarding timing.
(Possible that's EGR too, insufficient EGR flow will cause the engine to
tend to knock more.)
71: Engine coolant temperature was above 244° F. (Could be a bad CTS, or
wiring short..)